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  • Agile Development

    - by James Oloo Onyango
    Alot of literature has and is being written about agile developement and its surrounding philosophies. In my quest to find the best way to express the importance of agile methodologies, i have found Robert C. Martin's "A Satire Of Two Companies" to be both the most concise and thorough! Enjoy the read! Rufus Inc Project Kick Off Your name is Bob. The date is January 3, 2001, and your head still aches from the recent millennial revelry. You are sitting in a conference room with several managers and a group of your peers. You are a project team leader. Your boss is there, and he has brought along all of his team leaders. His boss called the meeting. "We have a new project to develop," says your boss's boss. Call him BB. The points in his hair are so long that they scrape the ceiling. Your boss's points are just starting to grow, but he eagerly awaits the day when he can leave Brylcream stains on the acoustic tiles. BB describes the essence of the new market they have identified and the product they want to develop to exploit this market. "We must have this new project up and working by fourth quarter October 1," BB demands. "Nothing is of higher priority, so we are cancelling your current project." The reaction in the room is stunned silence. Months of work are simply going to be thrown away. Slowly, a murmur of objection begins to circulate around the conference table.   His points give off an evil green glow as BB meets the eyes of everyone in the room. One by one, that insidious stare reduces each attendee to quivering lumps of protoplasm. It is clear that he will brook no discussion on this matter. Once silence has been restored, BB says, "We need to begin immediately. How long will it take you to do the analysis?" You raise your hand. Your boss tries to stop you, but his spitwad misses you and you are unaware of his efforts.   "Sir, we can't tell you how long the analysis will take until we have some requirements." "The requirements document won't be ready for 3 or 4 weeks," BB says, his points vibrating with frustration. "So, pretend that you have the requirements in front of you now. How long will you require for analysis?" No one breathes. Everyone looks around to see whether anyone has some idea. "If analysis goes beyond April 1, we have a problem. Can you finish the analysis by then?" Your boss visibly gathers his courage: "We'll find a way, sir!" His points grow 3 mm, and your headache increases by two Tylenol. "Good." BB smiles. "Now, how long will it take to do the design?" "Sir," you say. Your boss visibly pales. He is clearly worried that his 3 mms are at risk. "Without an analysis, it will not be possible to tell you how long design will take." BB's expression shifts beyond austere.   "PRETEND you have the analysis already!" he says, while fixing you with his vacant, beady little eyes. "How long will it take you to do the design?" Two Tylenol are not going to cut it. Your boss, in a desperate attempt to save his new growth, babbles: "Well, sir, with only six months left to complete the project, design had better take no longer than 3 months."   "I'm glad you agree, Smithers!" BB says, beaming. Your boss relaxes. He knows his points are secure. After a while, he starts lightly humming the Brylcream jingle. BB continues, "So, analysis will be complete by April 1, design will be complete by July 1, and that gives you 3 months to implement the project. This meeting is an example of how well our new consensus and empowerment policies are working. Now, get out there and start working. I'll expect to see TQM plans and QIT assignments on my desk by next week. Oh, and don't forget that your crossfunctional team meetings and reports will be needed for next month's quality audit." "Forget the Tylenol," you think to yourself as you return to your cubicle. "I need bourbon."   Visibly excited, your boss comes over to you and says, "Gosh, what a great meeting. I think we're really going to do some world shaking with this project." You nod in agreement, too disgusted to do anything else. "Oh," your boss continues, "I almost forgot." He hands you a 30-page document. "Remember that the SEI is coming to do an evaluation next week. This is the evaluation guide. You need to read through it, memorize it, and then shred it. It tells you how to answer any questions that the SEI auditors ask you. It also tells you what parts of the building you are allowed to take them to and what parts to avoid. We are determined to be a CMM level 3 organization by June!"   You and your peers start working on the analysis of the new project. This is difficult because you have no requirements. But from the 10-minute introduction given by BB on that fateful morning, you have some idea of what the product is supposed to do.   Corporate process demands that you begin by creating a use case document. You and your team begin enumerating use cases and drawing oval and stick diagrams. Philosophical debates break out among the team members. There is disagreement as to whether certain use cases should be connected with <<extends>> or <<includes>> relationships. Competing models are created, but nobody knows how to evaluate them. The debate continues, effectively paralyzing progress.   After a week, somebody finds the iceberg.com Web site, which recommends disposing entirely of <<extends>> and <<includes>> and replacing them with <<precedes>> and <<uses>>. The documents on this Web site, authored by Don Sengroiux, describes a method known as stalwart-analysis, which claims to be a step-by-step method for translating use cases into design diagrams. More competing use case models are created using this new scheme, but again, people can't agree on how to evaluate them. The thrashing continues. More and more, the use case meetings are driven by emotion rather than by reason. If it weren't for the fact that you don't have requirements, you'd be pretty upset by the lack of progress you are making. The requirements document arrives on February 15. And then again on February 20, 25, and every week thereafter. Each new version contradicts the previous one. Clearly, the marketing folks who are writing the requirements, empowered though they might be, are not finding consensus.   At the same time, several new competing use case templates have been proposed by the various team members. Each template presents its own particularly creative way of delaying progress. The debates rage on. On March 1, Prudence Putrigence, the process proctor, succeeds in integrating all the competing use case forms and templates into a single, all-encompassing form. Just the blank form is 15 pages long. She has managed to include every field that appeared on all the competing templates. She also presents a 159- page document describing how to fill out the use case form. All current use cases must be rewritten according to the new standard.   You marvel to yourself that it now requires 15 pages of fill-in-the-blank and essay questions to answer the question: What should the system do when the user presses Return? The corporate process (authored by L. E. Ott, famed author of "Holistic Analysis: A Progressive Dialectic for Software Engineers") insists that you discover all primary use cases, 87 percent of all secondary use cases, and 36.274 percent of all tertiary use cases before you can complete analysis and enter the design phase. You have no idea what a tertiary use case is. So in an attempt to meet this requirement, you try to get your use case document reviewed by the marketing department, which you hope will know what a tertiary use case is.   Unfortunately, the marketing folks are too busy with sales support to talk to you. Indeed, since the project started, you have not been able to get a single meeting with marketing, which has provided a never-ending stream of changing and contradictory requirements documents.   While one team has been spinning endlessly on the use case document, another team has been working out the domain model. Endless variations of UML documents are pouring out of this team. Every week, the model is reworked.   The team members can't decide whether to use <<interfaces>> or <<types>> in the model. A huge disagreement has been raging on the proper syntax and application of OCL. Others on the team just got back from a 5-day class on catabolism, and have been producing incredibly detailed and arcane diagrams that nobody else can fathom.   On March 27, with one week to go before analysis is to be complete, you have produced a sea of documents and diagrams but are no closer to a cogent analysis of the problem than you were on January 3. **** And then, a miracle happens.   **** On Saturday, April 1, you check your e-mail from home. You see a memo from your boss to BB. It states unequivocally that you are done with the analysis! You phone your boss and complain. "How could you have told BB that we were done with the analysis?" "Have you looked at a calendar lately?" he responds. "It's April 1!" The irony of that date does not escape you. "But we have so much more to think about. So much more to analyze! We haven't even decided whether to use <<extends>> or <<precedes>>!" "Where is your evidence that you are not done?" inquires your boss, impatiently. "Whaaa . . . ." But he cuts you off. "Analysis can go on forever; it has to be stopped at some point. And since this is the date it was scheduled to stop, it has been stopped. Now, on Monday, I want you to gather up all existing analysis materials and put them into a public folder. Release that folder to Prudence so that she can log it in the CM system by Monday afternoon. Then get busy and start designing."   As you hang up the phone, you begin to consider the benefits of keeping a bottle of bourbon in your bottom desk drawer. They threw a party to celebrate the on-time completion of the analysis phase. BB gave a colon-stirring speech on empowerment. And your boss, another 3 mm taller, congratulated his team on the incredible show of unity and teamwork. Finally, the CIO takes the stage to tell everyone that the SEI audit went very well and to thank everyone for studying and shredding the evaluation guides that were passed out. Level 3 now seems assured and will be awarded by June. (Scuttlebutt has it that managers at the level of BB and above are to receive significant bonuses once the SEI awards level 3.)   As the weeks flow by, you and your team work on the design of the system. Of course, you find that the analysis that the design is supposedly based on is flawedno, useless; no, worse than useless. But when you tell your boss that you need to go back and work some more on the analysis to shore up its weaker sections, he simply states, "The analysis phase is over. The only allowable activity is design. Now get back to it."   So, you and your team hack the design as best you can, unsure of whether the requirements have been properly analyzed. Of course, it really doesn't matter much, since the requirements document is still thrashing with weekly revisions, and the marketing department still refuses to meet with you.     The design is a nightmare. Your boss recently misread a book named The Finish Line in which the author, Mark DeThomaso, blithely suggested that design documents should be taken down to code-level detail. "If we are going to be working at that level of detail," you ask, "why don't we simply write the code instead?" "Because then you wouldn't be designing, of course. And the only allowable activity in the design phase is design!" "Besides," he continues, "we have just purchased a companywide license for Dandelion! This tool enables 'Round the Horn Engineering!' You are to transfer all design diagrams into this tool. It will automatically generate our code for us! It will also keep the design diagrams in sync with the code!" Your boss hands you a brightly colored shrinkwrapped box containing the Dandelion distribution. You accept it numbly and shuffle off to your cubicle. Twelve hours, eight crashes, one disk reformatting, and eight shots of 151 later, you finally have the tool installed on your server. You consider the week your team will lose while attending Dandelion training. Then you smile and think, "Any week I'm not here is a good week." Design diagram after design diagram is created by your team. Dandelion makes it very difficult to draw these diagrams. There are dozens and dozens of deeply nested dialog boxes with funny text fields and check boxes that must all be filled in correctly. And then there's the problem of moving classes between packages. At first, these diagram are driven from the use cases. But the requirements are changing so often that the use cases rapidly become meaningless. Debates rage about whether VISITOR or DECORATOR design patterns should be used. One developer refuses to use VISITOR in any form, claiming that it's not a properly object-oriented construct. Someone refuses to use multiple inheritance, since it is the spawn of the devil. Review meetings rapidly degenerate into debates about the meaning of object orientation, the definition of analysis versus design, or when to use aggregation versus association. Midway through the design cycle, the marketing folks announce that they have rethought the focus of the system. Their new requirements document is completely restructured. They have eliminated several major feature areas and replaced them with feature areas that they anticipate customer surveys will show to be more appropriate. You tell your boss that these changes mean that you need to reanalyze and redesign much of the system. But he says, "The analysis phase is system. But he says, "The analysis phase is over. The only allowable activity is design. Now get back to it."   You suggest that it might be better to create a simple prototype to show to the marketing folks and even some potential customers. But your boss says, "The analysis phase is over. The only allowable activity is design. Now get back to it." Hack, hack, hack, hack. You try to create some kind of a design document that might reflect the new requirements documents. However, the revolution of the requirements has not caused them to stop thrashing. Indeed, if anything, the wild oscillations of the requirements document have only increased in frequency and amplitude.   You slog your way through them.   On June 15, the Dandelion database gets corrupted. Apparently, the corruption has been progressive. Small errors in the DB accumulated over the months into bigger and bigger errors. Eventually, the CASE tool just stopped working. Of course, the slowly encroaching corruption is present on all the backups. Calls to the Dandelion technical support line go unanswered for several days. Finally, you receive a brief e-mail from Dandelion, informing you that this is a known problem and that the solution is to purchase the new version, which they promise will be ready some time next quarter, and then reenter all the diagrams by hand.   ****   Then, on July 1 another miracle happens! You are done with the design!   Rather than go to your boss and complain, you stock your middle desk drawer with some vodka.   **** They threw a party to celebrate the on-time completion of the design phase and their graduation to CMM level 3. This time, you find BB's speech so stirring that you have to use the restroom before it begins. New banners and plaques are all over your workplace. They show pictures of eagles and mountain climbers, and they talk about teamwork and empowerment. They read better after a few scotches. That reminds you that you need to clear out your file cabinet to make room for the brandy. You and your team begin to code. But you rapidly discover that the design is lacking in some significant areas. Actually, it's lacking any significance at all. You convene a design session in one of the conference rooms to try to work through some of the nastier problems. But your boss catches you at it and disbands the meeting, saying, "The design phase is over. The only allowable activity is coding. Now get back to it."   ****   The code generated by Dandelion is really hideous. It turns out that you and your team were using association and aggregation the wrong way, after all. All the generated code has to be edited to correct these flaws. Editing this code is extremely difficult because it has been instrumented with ugly comment blocks that have special syntax that Dandelion needs in order to keep the diagrams in sync with the code. If you accidentally alter one of these comments, the diagrams will be regenerated incorrectly. It turns out that "Round the Horn Engineering" requires an awful lot of effort. The more you try to keep the code compatible with Dandelion, the more errors Dandelion generates. In the end, you give up and decide to keep the diagrams up to date manually. A second later, you decide that there's no point in keeping the diagrams up to date at all. Besides, who has time?   Your boss hires a consultant to build tools to count the number of lines of code that are being produced. He puts a big thermometer graph on the wall with the number 1,000,000 on the top. Every day, he extends the red line to show how many lines have been added. Three days after the thermometer appears on the wall, your boss stops you in the hall. "That graph isn't growing quickly enough. We need to have a million lines done by October 1." "We aren't even sh-sh-sure that the proshect will require a m-million linezh," you blather. "We have to have a million lines done by October 1," your boss reiterates. His points have grown again, and the Grecian formula he uses on them creates an aura of authority and competence. "Are you sure your comment blocks are big enough?" Then, in a flash of managerial insight, he says, "I have it! I want you to institute a new policy among the engineers. No line of code is to be longer than 20 characters. Any such line must be split into two or more preferably more. All existing code needs to be reworked to this standard. That'll get our line count up!"   You decide not to tell him that this will require two unscheduled work months. You decide not to tell him anything at all. You decide that intravenous injections of pure ethanol are the only solution. You make the appropriate arrangements. Hack, hack, hack, and hack. You and your team madly code away. By August 1, your boss, frowning at the thermometer on the wall, institutes a mandatory 50-hour workweek.   Hack, hack, hack, and hack. By September 1st, the thermometer is at 1.2 million lines and your boss asks you to write a report describing why you exceeded the coding budget by 20 percent. He institutes mandatory Saturdays and demands that the project be brought back down to a million lines. You start a campaign of remerging lines. Hack, hack, hack, and hack. Tempers are flaring; people are quitting; QA is raining trouble reports down on you. Customers are demanding installation and user manuals; salespeople are demanding advance demonstrations for special customers; the requirements document is still thrashing, the marketing folks are complaining that the product isn't anything like they specified, and the liquor store won't accept your credit card anymore. Something has to give.    On September 15, BB calls a meeting. As he enters the room, his points are emitting clouds of steam. When he speaks, the bass overtones of his carefully manicured voice cause the pit of your stomach to roll over. "The QA manager has told me that this project has less than 50 percent of the required features implemented. He has also informed me that the system crashes all the time, yields wrong results, and is hideously slow. He has also complained that he cannot keep up with the continuous train of daily releases, each more buggy than the last!" He stops for a few seconds, visibly trying to compose himself. "The QA manager estimates that, at this rate of development, we won't be able to ship the product until December!" Actually, you think it's more like March, but you don't say anything. "December!" BB roars with such derision that people duck their heads as though he were pointing an assault rifle at them. "December is absolutely out of the question. Team leaders, I want new estimates on my desk in the morning. I am hereby mandating 65-hour work weeks until this project is complete. And it better be complete by November 1."   As he leaves the conference room, he is heard to mutter: "Empowermentbah!" * * * Your boss is bald; his points are mounted on BB's wall. The fluorescent lights reflecting off his pate momentarily dazzle you. "Do you have anything to drink?" he asks. Having just finished your last bottle of Boone's Farm, you pull a bottle of Thunderbird from your bookshelf and pour it into his coffee mug. "What's it going to take to get this project done? " he asks. "We need to freeze the requirements, analyze them, design them, and then implement them," you say callously. "By November 1?" your boss exclaims incredulously. "No way! Just get back to coding the damned thing." He storms out, scratching his vacant head.   A few days later, you find that your boss has been transferred to the corporate research division. Turnover has skyrocketed. Customers, informed at the last minute that their orders cannot be fulfilled on time, have begun to cancel their orders. Marketing is re-evaluating whether this product aligns with the overall goals of the company. Memos fly, heads roll, policies change, and things are, overall, pretty grim. Finally, by March, after far too many sixty-five hour weeks, a very shaky version of the software is ready. In the field, bug-discovery rates are high, and the technical support staff are at their wits' end, trying to cope with the complaints and demands of the irate customers. Nobody is happy.   In April, BB decides to buy his way out of the problem by licensing a product produced by Rupert Industries and redistributing it. The customers are mollified, the marketing folks are smug, and you are laid off.     Rupert Industries: Project Alpha   Your name is Robert. The date is January 3, 2001. The quiet hours spent with your family this holiday have left you refreshed and ready for work. You are sitting in a conference room with your team of professionals. The manager of the division called the meeting. "We have some ideas for a new project," says the division manager. Call him Russ. He is a high-strung British chap with more energy than a fusion reactor. He is ambitious and driven but understands the value of a team. Russ describes the essence of the new market opportunity the company has identified and introduces you to Jane, the marketing manager, who is responsible for defining the products that will address it. Addressing you, Jane says, "We'd like to start defining our first product offering as soon as possible. When can you and your team meet with me?" You reply, "We'll be done with the current iteration of our project this Friday. We can spare a few hours for you between now and then. After that, we'll take a few people from the team and dedicate them to you. We'll begin hiring their replacements and the new people for your team immediately." "Great," says Russ, "but I want you to understand that it is critical that we have something to exhibit at the trade show coming up this July. If we can't be there with something significant, we'll lose the opportunity."   "I understand," you reply. "I don't yet know what it is that you have in mind, but I'm sure we can have something by July. I just can't tell you what that something will be right now. In any case, you and Jane are going to have complete control over what we developers do, so you can rest assured that by July, you'll have the most important things that can be accomplished in that time ready to exhibit."   Russ nods in satisfaction. He knows how this works. Your team has always kept him advised and allowed him to steer their development. He has the utmost confidence that your team will work on the most important things first and will produce a high-quality product.   * * *   "So, Robert," says Jane at their first meeting, "How does your team feel about being split up?" "We'll miss working with each other," you answer, "but some of us were getting pretty tired of that last project and are looking forward to a change. So, what are you people cooking up?" Jane beams. "You know how much trouble our customers currently have . . ." And she spends a half hour or so describing the problem and possible solution. "OK, wait a second" you respond. "I need to be clear about this." And so you and Jane talk about how this system might work. Some of her ideas aren't fully formed. You suggest possible solutions. She likes some of them. You continue discussing.   During the discussion, as each new topic is addressed, Jane writes user story cards. Each card represents something that the new system has to do. The cards accumulate on the table and are spread out in front of you. Both you and Jane point at them, pick them up, and make notes on them as you discuss the stories. The cards are powerful mnemonic devices that you can use to represent complex ideas that are barely formed.   At the end of the meeting, you say, "OK, I've got a general idea of what you want. I'm going to talk to the team about it. I imagine they'll want to run some experiments with various database structures and presentation formats. Next time we meet, it'll be as a group, and we'll start identifying the most important features of the system."   A week later, your nascent team meets with Jane. They spread the existing user story cards out on the table and begin to get into some of the details of the system. The meeting is very dynamic. Jane presents the stories in the order of their importance. There is much discussion about each one. The developers are concerned about keeping the stories small enough to estimate and test. So they continually ask Jane to split one story into several smaller stories. Jane is concerned that each story have a clear business value and priority, so as she splits them, she makes sure that this stays true.   The stories accumulate on the table. Jane writes them, but the developers make notes on them as needed. Nobody tries to capture everything that is said; the cards are not meant to capture everything but are simply reminders of the conversation.   As the developers become more comfortable with the stories, they begin writing estimates on them. These estimates are crude and budgetary, but they give Jane an idea of what the story will cost.   At the end of the meeting, it is clear that many more stories could be discussed. It is also clear that the most important stories have been addressed and that they represent several months worth of work. Jane closes the meeting by taking the cards with her and promising to have a proposal for the first release in the morning.   * * *   The next morning, you reconvene the meeting. Jane chooses five cards and places them on the table. "According to your estimates, these cards represent about one perfect team-week's worth of work. The last iteration of the previous project managed to get one perfect team-week done in 3 real weeks. If we can get these five stories done in 3 weeks, we'll be able to demonstrate them to Russ. That will make him feel very comfortable about our progress." Jane is pushing it. The sheepish look on her face lets you know that she knows it too. You reply, "Jane, this is a new team, working on a new project. It's a bit presumptuous to expect that our velocity will be the same as the previous team's. However, I met with the team yesterday afternoon, and we all agreed that our initial velocity should, in fact, be set to one perfectweek for every 3 real-weeks. So you've lucked out on this one." "Just remember," you continue, "that the story estimates and the story velocity are very tentative at this point. We'll learn more when we plan the iteration and even more when we implement it."   Jane looks over her glasses at you as if to say "Who's the boss around here, anyway?" and then smiles and says, "Yeah, don't worry. I know the drill by now."Jane then puts 15 more cards on the table. She says, "If we can get all these cards done by the end of March, we can turn the system over to our beta test customers. And we'll get good feedback from them."   You reply, "OK, so we've got our first iteration defined, and we have the stories for the next three iterations after that. These four iterations will make our first release."   "So," says Jane, can you really do these five stories in the next 3 weeks?" "I don't know for sure, Jane," you reply. "Let's break them down into tasks and see what we get."   So Jane, you, and your team spend the next several hours taking each of the five stories that Jane chose for the first iteration and breaking them down into small tasks. The developers quickly realize that some of the tasks can be shared between stories and that other tasks have commonalities that can probably be taken advantage of. It is clear that potential designs are popping into the developers' heads. From time to time, they form little discussion knots and scribble UML diagrams on some cards.   Soon, the whiteboard is filled with the tasks that, once completed, will implement the five stories for this iteration. You start the sign-up process by saying, "OK, let's sign up for these tasks." "I'll take the initial database generation." Says Pete. "That's what I did on the last project, and this doesn't look very different. I estimate it at two of my perfect workdays." "OK, well, then, I'll take the login screen," says Joe. "Aw, darn," says Elaine, the junior member of the team, "I've never done a GUI, and kinda wanted to try that one."   "Ah, the impatience of youth," Joe says sagely, with a wink in your direction. "You can assist me with it, young Jedi." To Jane: "I think it'll take me about three of my perfect workdays."   One by one, the developers sign up for tasks and estimate them in terms of their own perfect workdays. Both you and Jane know that it is best to let the developers volunteer for tasks than to assign the tasks to them. You also know full well that you daren't challenge any of the developers' estimates. You know these people, and you trust them. You know that they are going to do the very best they can.   The developers know that they can't sign up for more perfect workdays than they finished in the last iteration they worked on. Once each developer has filled his or her schedule for the iteration, they stop signing up for tasks.   Eventually, all the developers have stopped signing up for tasks. But, of course, tasks are still left on the board.   "I was worried that that might happen," you say, "OK, there's only one thing to do, Jane. We've got too much to do in this iteration. What stories or tasks can we remove?" Jane sighs. She knows that this is the only option. Working overtime at the beginning of a project is insane, and projects where she's tried it have not fared well.   So Jane starts to remove the least-important functionality. "Well, we really don't need the login screen just yet. We can simply start the system in the logged-in state." "Rats!" cries Elaine. "I really wanted to do that." "Patience, grasshopper." says Joe. "Those who wait for the bees to leave the hive will not have lips too swollen to relish the honey." Elaine looks confused. Everyone looks confused. "So . . .," Jane continues, "I think we can also do away with . . ." And so, bit by bit, the list of tasks shrinks. Developers who lose a task sign up for one of the remaining ones.   The negotiation is not painless. Several times, Jane exhibits obvious frustration and impatience. Once, when tensions are especially high, Elaine volunteers, "I'll work extra hard to make up some of the missing time." You are about to correct her when, fortunately, Joe looks her in the eye and says, "When once you proceed down the dark path, forever will it dominate your destiny."   In the end, an iteration acceptable to Jane is reached. It's not what Jane wanted. Indeed, it is significantly less. But it's something the team feels that can be achieved in the next 3 weeks.   And, after all, it still addresses the most important things that Jane wanted in the iteration. "So, Jane," you say when things had quieted down a bit, "when can we expect acceptance tests from you?" Jane sighs. This is the other side of the coin. For every story the development team implements,   Jane must supply a suite of acceptance tests that prove that it works. And the team needs these long before the end of the iteration, since they will certainly point out differences in the way Jane and the developers imagine the system's behaviour.   "I'll get you some example test scripts today," Jane promises. "I'll add to them every day after that. You'll have the entire suite by the middle of the iteration."   * * *   The iteration begins on Monday morning with a flurry of Class, Responsibilities, Collaborators sessions. By midmorning, all the developers have assembled into pairs and are rapidly coding away. "And now, my young apprentice," Joe says to Elaine, "you shall learn the mysteries of test-first design!"   "Wow, that sounds pretty rad," Elaine replies. "How do you do it?" Joe beams. It's clear that he has been anticipating this moment. "OK, what does the code do right now?" "Huh?" replied Elaine, "It doesn't do anything at all; there is no code."   "So, consider our task; can you think of something the code should do?" "Sure," Elaine said with youthful assurance, "First, it should connect to the database." "And thereupon, what must needs be required to connecteth the database?" "You sure talk weird," laughed Elaine. "I think we'd have to get the database object from some registry and call the Connect() method. "Ah, astute young wizard. Thou perceives correctly that we requireth an object within which we can cacheth the database object." "Is 'cacheth' really a word?" "It is when I say it! So, what test can we write that we know the database registry should pass?" Elaine sighs. She knows she'll just have to play along. "We should be able to create a database object and pass it to the registry in a Store() method. And then we should be able to pull it out of the registry with a Get() method and make sure it's the same object." "Oh, well said, my prepubescent sprite!" "Hay!" "So, now, let's write a test function that proves your case." "But shouldn't we write the database object and registry object first?" "Ah, you've much to learn, my young impatient one. Just write the test first." "But it won't even compile!" "Are you sure? What if it did?" "Uh . . ." "Just write the test, Elaine. Trust me." And so Joe, Elaine, and all the other developers began to code their tasks, one test case at a time. The room in which they worked was abuzz with the conversations between the pairs. The murmur was punctuated by an occasional high five when a pair managed to finish a task or a difficult test case.   As development proceeded, the developers changed partners once or twice a day. Each developer got to see what all the others were doing, and so knowledge of the code spread generally throughout the team.   Whenever a pair finished something significant whether a whole task or simply an important part of a task they integrated what they had with the rest of the system. Thus, the code base grew daily, and integration difficulties were minimized.   The developers communicated with Jane on a daily basis. They'd go to her whenever they had a question about the functionality of the system or the interpretation of an acceptance test case.   Jane, good as her word, supplied the team with a steady stream of acceptance test scripts. The team read these carefully and thereby gained a much better understanding of what Jane expected the system to do. By the beginning of the second week, there was enough functionality to demonstrate to Jane. She watched eagerly as the demonstration passed test case after test case. "This is really cool," Jane said as the demonstration finally ended. "But this doesn't seem like one-third of the tasks. Is your velocity slower than anticipated?"   You grimace. You'd been waiting for a good time to mention this to Jane but now she was forcing the issue. "Yes, unfortunately, we are going more slowly than we had expected. The new application server we are using is turning out to be a pain to configure. Also, it takes forever to reboot, and we have to reboot it whenever we make even the slightest change to its configuration."   Jane eyes you with suspicion. The stress of last Monday's negotiations had still not entirely dissipated. She says, "And what does this mean to our schedule? We can't slip it again, we just can't. Russ will have a fit! He'll haul us all into the woodshed and ream us some new ones."   You look Jane right in the eyes. There's no pleasant way to give someone news like this. So you just blurt out, "Look, if things keep going like they're going, we're not going to be done with everything by next Friday. Now it's possible that we'll figure out a way to go faster. But, frankly, I wouldn't depend on that. You should start thinking about one or two tasks that could be removed from the iteration without ruining the demonstration for Russ. Come hell or high water, we are going to give that demonstration on Friday, and I don't think you want us to choose which tasks to omit."   "Aw forchrisakes!" Jane barely manages to stifle yelling that last word as she stalks away, shaking her head. Not for the first time, you say to yourself, "Nobody ever promised me project management would be easy." You are pretty sure it won't be the last time, either.   Actually, things went a bit better than you had hoped. The team did, in fact, have to drop one task from the iteration, but Jane had chosen wisely, and the demonstration for Russ went without a hitch. Russ was not impressed with the progress, but neither was he dismayed. He simply said, "This is pretty good. But remember, we have to be able to demonstrate this system at the trade show in July, and at this rate, it doesn't look like you'll have all that much to show." Jane, whose attitude had improved dramatically with the completion of the iteration, responded to Russ by saying, "Russ, this team is working hard, and well. When July comes around, I am confident that we'll have something significant to demonstrate. It won't be everything, and some of it may be smoke and mirrors, but we'll have something."   Painful though the last iteration was, it had calibrated your velocity numbers. The next iteration went much better. Not because your team got more done than in the last iteration but simply because the team didn't have to remove any tasks or stories in the middle of the iteration.   By the start of the fourth iteration, a natural rhythm has been established. Jane, you, and the team know exactly what to expect from one another. The team is running hard, but the pace is sustainable. You are confident that the team can keep up this pace for a year or more.   The number of surprises in the schedule diminishes to near zero; however, the number of surprises in the requirements does not. Jane and Russ frequently look over the growing system and make recommendations or changes to the existing functionality. But all parties realize that these changes take time and must be scheduled. So the changes do not cause anyone's expectations to be violated. In March, there is a major demonstration of the system to the board of directors. The system is very limited and is not yet in a form good enough to take to the trade show, but progress is steady, and the board is reasonably impressed.   The second release goes even more smoothly than the first. By now, the team has figured out a way to automate Jane's acceptance test scripts. The team has also refactored the design of the system to the point that it is really easy to add new features and change old ones. The second release was done by the end of June and was taken to the trade show. It had less in it than Jane and Russ would have liked, but it did demonstrate the most important features of the system. Although customers at the trade show noticed that certain features were missing, they were very impressed overall. You, Russ, and Jane all returned from the trade show with smiles on your faces. You all felt as though this project was a winner.   Indeed, many months later, you are contacted by Rufus Inc. That company had been working on a system like this for its internal operations. Rufus has canceled the development of that system after a death-march project and is negotiating to license your technology for its environment.   Indeed, things are looking up!

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  • New features of C# 4.0

    This article covers New features of C# 4.0. Article has been divided into below sections. Introduction. Dynamic Lookup. Named and Optional Arguments. Features for COM interop. Variance. Relationship with Visual Basic. Resources. Other interested readings… 22 New Features of Visual Studio 2008 for .NET Professionals 50 New Features of SQL Server 2008 IIS 7.0 New features Introduction It is now close to a year since Microsoft Visual C# 3.0 shipped as part of Visual Studio 2008. In the VS Managed Languages team we are hard at work on creating the next version of the language (with the unsurprising working title of C# 4.0), and this document is a first public description of the planned language features as we currently see them. Please be advised that all this is in early stages of production and is subject to change. Part of the reason for sharing our plans in public so early is precisely to get the kind of feedback that will cause us to improve the final product before it rolls out. Simultaneously with the publication of this whitepaper, a first public CTP (community technology preview) of Visual Studio 2010 is going out as a Virtual PC image for everyone to try. Please use it to play and experiment with the features, and let us know of any thoughts you have. We ask for your understanding and patience working with very early bits, where especially new or newly implemented features do not have the quality or stability of a final product. The aim of the CTP is not to give you a productive work environment but to give you the best possible impression of what we are working on for the next release. The CTP contains a number of walkthroughs, some of which highlight the new language features of C# 4.0. Those are excellent for getting a hands-on guided tour through the details of some common scenarios for the features. You may consider this whitepaper a companion document to these walkthroughs, complementing them with a focus on the overall language features and how they work, as opposed to the specifics of the concrete scenarios. C# 4.0 The major theme for C# 4.0 is dynamic programming. Increasingly, objects are “dynamic” in the sense that their structure and behavior is not captured by a static type, or at least not one that the compiler knows about when compiling your program. Some examples include a. objects from dynamic programming languages, such as Python or Ruby b. COM objects accessed through IDispatch c. ordinary .NET types accessed through reflection d. objects with changing structure, such as HTML DOM objects While C# remains a statically typed language, we aim to vastly improve the interaction with such objects. A secondary theme is co-evolution with Visual Basic. Going forward we will aim to maintain the individual character of each language, but at the same time important new features should be introduced in both languages at the same time. They should be differentiated more by style and feel than by feature set. The new features in C# 4.0 fall into four groups: Dynamic lookup Dynamic lookup allows you to write method, operator and indexer calls, property and field accesses, and even object invocations which bypass the C# static type checking and instead gets resolved at runtime. Named and optional parameters Parameters in C# can now be specified as optional by providing a default value for them in a member declaration. When the member is invoked, optional arguments can be omitted. Furthermore, any argument can be passed by parameter name instead of position. COM specific interop features Dynamic lookup as well as named and optional parameters both help making programming against COM less painful than today. On top of that, however, we are adding a number of other small features that further improve the interop experience. Variance It used to be that an IEnumerable<string> wasn’t an IEnumerable<object>. Now it is – C# embraces type safe “co-and contravariance” and common BCL types are updated to take advantage of that. Dynamic Lookup Dynamic lookup allows you a unified approach to invoking things dynamically. With dynamic lookup, when you have an object in your hand you do not need to worry about whether it comes from COM, IronPython, the HTML DOM or reflection; you just apply operations to it and leave it to the runtime to figure out what exactly those operations mean for that particular object. This affords you enormous flexibility, and can greatly simplify your code, but it does come with a significant drawback: Static typing is not maintained for these operations. A dynamic object is assumed at compile time to support any operation, and only at runtime will you get an error if it wasn’t so. Oftentimes this will be no loss, because the object wouldn’t have a static type anyway, in other cases it is a tradeoff between brevity and safety. In order to facilitate this tradeoff, it is a design goal of C# to allow you to opt in or opt out of dynamic behavior on every single call. The dynamic type C# 4.0 introduces a new static type called dynamic. When you have an object of type dynamic you can “do things to it” that are resolved only at runtime: dynamic d = GetDynamicObject(…); d.M(7); The C# compiler allows you to call a method with any name and any arguments on d because it is of type dynamic. At runtime the actual object that d refers to will be examined to determine what it means to “call M with an int” on it. The type dynamic can be thought of as a special version of the type object, which signals that the object can be used dynamically. It is easy to opt in or out of dynamic behavior: any object can be implicitly converted to dynamic, “suspending belief” until runtime. Conversely, there is an “assignment conversion” from dynamic to any other type, which allows implicit conversion in assignment-like constructs: dynamic d = 7; // implicit conversion int i = d; // assignment conversion Dynamic operations Not only method calls, but also field and property accesses, indexer and operator calls and even delegate invocations can be dispatched dynamically: dynamic d = GetDynamicObject(…); d.M(7); // calling methods d.f = d.P; // getting and settings fields and properties d[“one”] = d[“two”]; // getting and setting thorugh indexers int i = d + 3; // calling operators string s = d(5,7); // invoking as a delegate The role of the C# compiler here is simply to package up the necessary information about “what is being done to d”, so that the runtime can pick it up and determine what the exact meaning of it is given an actual object d. Think of it as deferring part of the compiler’s job to runtime. The result of any dynamic operation is itself of type dynamic. Runtime lookup At runtime a dynamic operation is dispatched according to the nature of its target object d: COM objects If d is a COM object, the operation is dispatched dynamically through COM IDispatch. This allows calling to COM types that don’t have a Primary Interop Assembly (PIA), and relying on COM features that don’t have a counterpart in C#, such as indexed properties and default properties. Dynamic objects If d implements the interface IDynamicObject d itself is asked to perform the operation. Thus by implementing IDynamicObject a type can completely redefine the meaning of dynamic operations. This is used intensively by dynamic languages such as IronPython and IronRuby to implement their own dynamic object models. It will also be used by APIs, e.g. by the HTML DOM to allow direct access to the object’s properties using property syntax. Plain objects Otherwise d is a standard .NET object, and the operation will be dispatched using reflection on its type and a C# “runtime binder” which implements C#’s lookup and overload resolution semantics at runtime. This is essentially a part of the C# compiler running as a runtime component to “finish the work” on dynamic operations that was deferred by the static compiler. Example Assume the following code: dynamic d1 = new Foo(); dynamic d2 = new Bar(); string s; d1.M(s, d2, 3, null); Because the receiver of the call to M is dynamic, the C# compiler does not try to resolve the meaning of the call. Instead it stashes away information for the runtime about the call. This information (often referred to as the “payload”) is essentially equivalent to: “Perform an instance method call of M with the following arguments: 1. a string 2. a dynamic 3. a literal int 3 4. a literal object null” At runtime, assume that the actual type Foo of d1 is not a COM type and does not implement IDynamicObject. In this case the C# runtime binder picks up to finish the overload resolution job based on runtime type information, proceeding as follows: 1. Reflection is used to obtain the actual runtime types of the two objects, d1 and d2, that did not have a static type (or rather had the static type dynamic). The result is Foo for d1 and Bar for d2. 2. Method lookup and overload resolution is performed on the type Foo with the call M(string,Bar,3,null) using ordinary C# semantics. 3. If the method is found it is invoked; otherwise a runtime exception is thrown. Overload resolution with dynamic arguments Even if the receiver of a method call is of a static type, overload resolution can still happen at runtime. This can happen if one or more of the arguments have the type dynamic: Foo foo = new Foo(); dynamic d = new Bar(); var result = foo.M(d); The C# runtime binder will choose between the statically known overloads of M on Foo, based on the runtime type of d, namely Bar. The result is again of type dynamic. The Dynamic Language Runtime An important component in the underlying implementation of dynamic lookup is the Dynamic Language Runtime (DLR), which is a new API in .NET 4.0. The DLR provides most of the infrastructure behind not only C# dynamic lookup but also the implementation of several dynamic programming languages on .NET, such as IronPython and IronRuby. Through this common infrastructure a high degree of interoperability is ensured, but just as importantly the DLR provides excellent caching mechanisms which serve to greatly enhance the efficiency of runtime dispatch. To the user of dynamic lookup in C#, the DLR is invisible except for the improved efficiency. However, if you want to implement your own dynamically dispatched objects, the IDynamicObject interface allows you to interoperate with the DLR and plug in your own behavior. This is a rather advanced task, which requires you to understand a good deal more about the inner workings of the DLR. For API writers, however, it can definitely be worth the trouble in order to vastly improve the usability of e.g. a library representing an inherently dynamic domain. Open issues There are a few limitations and things that might work differently than you would expect. · The DLR allows objects to be created from objects that represent classes. However, the current implementation of C# doesn’t have syntax to support this. · Dynamic lookup will not be able to find extension methods. Whether extension methods apply or not depends on the static context of the call (i.e. which using clauses occur), and this context information is not currently kept as part of the payload. · Anonymous functions (i.e. lambda expressions) cannot appear as arguments to a dynamic method call. The compiler cannot bind (i.e. “understand”) an anonymous function without knowing what type it is converted to. One consequence of these limitations is that you cannot easily use LINQ queries over dynamic objects: dynamic collection = …; var result = collection.Select(e => e + 5); If the Select method is an extension method, dynamic lookup will not find it. Even if it is an instance method, the above does not compile, because a lambda expression cannot be passed as an argument to a dynamic operation. There are no plans to address these limitations in C# 4.0. Named and Optional Arguments Named and optional parameters are really two distinct features, but are often useful together. Optional parameters allow you to omit arguments to member invocations, whereas named arguments is a way to provide an argument using the name of the corresponding parameter instead of relying on its position in the parameter list. Some APIs, most notably COM interfaces such as the Office automation APIs, are written specifically with named and optional parameters in mind. Up until now it has been very painful to call into these APIs from C#, with sometimes as many as thirty arguments having to be explicitly passed, most of which have reasonable default values and could be omitted. Even in APIs for .NET however you sometimes find yourself compelled to write many overloads of a method with different combinations of parameters, in order to provide maximum usability to the callers. Optional parameters are a useful alternative for these situations. Optional parameters A parameter is declared optional simply by providing a default value for it: public void M(int x, int y = 5, int z = 7); Here y and z are optional parameters and can be omitted in calls: M(1, 2, 3); // ordinary call of M M(1, 2); // omitting z – equivalent to M(1, 2, 7) M(1); // omitting both y and z – equivalent to M(1, 5, 7) Named and optional arguments C# 4.0 does not permit you to omit arguments between commas as in M(1,,3). This could lead to highly unreadable comma-counting code. Instead any argument can be passed by name. Thus if you want to omit only y from a call of M you can write: M(1, z: 3); // passing z by name or M(x: 1, z: 3); // passing both x and z by name or even M(z: 3, x: 1); // reversing the order of arguments All forms are equivalent, except that arguments are always evaluated in the order they appear, so in the last example the 3 is evaluated before the 1. Optional and named arguments can be used not only with methods but also with indexers and constructors. Overload resolution Named and optional arguments affect overload resolution, but the changes are relatively simple: A signature is applicable if all its parameters are either optional or have exactly one corresponding argument (by name or position) in the call which is convertible to the parameter type. Betterness rules on conversions are only applied for arguments that are explicitly given – omitted optional arguments are ignored for betterness purposes. If two signatures are equally good, one that does not omit optional parameters is preferred. M(string s, int i = 1); M(object o); M(int i, string s = “Hello”); M(int i); M(5); Given these overloads, we can see the working of the rules above. M(string,int) is not applicable because 5 doesn’t convert to string. M(int,string) is applicable because its second parameter is optional, and so, obviously are M(object) and M(int). M(int,string) and M(int) are both better than M(object) because the conversion from 5 to int is better than the conversion from 5 to object. Finally M(int) is better than M(int,string) because no optional arguments are omitted. Thus the method that gets called is M(int). Features for COM interop Dynamic lookup as well as named and optional parameters greatly improve the experience of interoperating with COM APIs such as the Office Automation APIs. In order to remove even more of the speed bumps, a couple of small COM-specific features are also added to C# 4.0. Dynamic import Many COM methods accept and return variant types, which are represented in the PIAs as object. In the vast majority of cases, a programmer calling these methods already knows the static type of a returned object from context, but explicitly has to perform a cast on the returned value to make use of that knowledge. These casts are so common that they constitute a major nuisance. In order to facilitate a smoother experience, you can now choose to import these COM APIs in such a way that variants are instead represented using the type dynamic. In other words, from your point of view, COM signatures now have occurrences of dynamic instead of object in them. This means that you can easily access members directly off a returned object, or you can assign it to a strongly typed local variable without having to cast. To illustrate, you can now say excel.Cells[1, 1].Value = "Hello"; instead of ((Excel.Range)excel.Cells[1, 1]).Value2 = "Hello"; and Excel.Range range = excel.Cells[1, 1]; instead of Excel.Range range = (Excel.Range)excel.Cells[1, 1]; Compiling without PIAs Primary Interop Assemblies are large .NET assemblies generated from COM interfaces to facilitate strongly typed interoperability. They provide great support at design time, where your experience of the interop is as good as if the types where really defined in .NET. However, at runtime these large assemblies can easily bloat your program, and also cause versioning issues because they are distributed independently of your application. The no-PIA feature allows you to continue to use PIAs at design time without having them around at runtime. Instead, the C# compiler will bake the small part of the PIA that a program actually uses directly into its assembly. At runtime the PIA does not have to be loaded. Omitting ref Because of a different programming model, many COM APIs contain a lot of reference parameters. Contrary to refs in C#, these are typically not meant to mutate a passed-in argument for the subsequent benefit of the caller, but are simply another way of passing value parameters. It therefore seems unreasonable that a C# programmer should have to create temporary variables for all such ref parameters and pass these by reference. Instead, specifically for COM methods, the C# compiler will allow you to pass arguments by value to such a method, and will automatically generate temporary variables to hold the passed-in values, subsequently discarding these when the call returns. In this way the caller sees value semantics, and will not experience any side effects, but the called method still gets a reference. Open issues A few COM interface features still are not surfaced in C#. Most notably these include indexed properties and default properties. As mentioned above these will be respected if you access COM dynamically, but statically typed C# code will still not recognize them. There are currently no plans to address these remaining speed bumps in C# 4.0. Variance An aspect of generics that often comes across as surprising is that the following is illegal: IList<string> strings = new List<string>(); IList<object> objects = strings; The second assignment is disallowed because strings does not have the same element type as objects. There is a perfectly good reason for this. If it were allowed you could write: objects[0] = 5; string s = strings[0]; Allowing an int to be inserted into a list of strings and subsequently extracted as a string. This would be a breach of type safety. However, there are certain interfaces where the above cannot occur, notably where there is no way to insert an object into the collection. Such an interface is IEnumerable<T>. If instead you say: IEnumerable<object> objects = strings; There is no way we can put the wrong kind of thing into strings through objects, because objects doesn’t have a method that takes an element in. Variance is about allowing assignments such as this in cases where it is safe. The result is that a lot of situations that were previously surprising now just work. Covariance In .NET 4.0 the IEnumerable<T> interface will be declared in the following way: public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IEnumerator { bool MoveNext(); T Current { get; } } The “out” in these declarations signifies that the T can only occur in output position in the interface – the compiler will complain otherwise. In return for this restriction, the interface becomes “covariant” in T, which means that an IEnumerable<A> is considered an IEnumerable<B> if A has a reference conversion to B. As a result, any sequence of strings is also e.g. a sequence of objects. This is useful e.g. in many LINQ methods. Using the declarations above: var result = strings.Union(objects); // succeeds with an IEnumerable<object> This would previously have been disallowed, and you would have had to to some cumbersome wrapping to get the two sequences to have the same element type. Contravariance Type parameters can also have an “in” modifier, restricting them to occur only in input positions. An example is IComparer<T>: public interface IComparer<in T> { public int Compare(T left, T right); } The somewhat baffling result is that an IComparer<object> can in fact be considered an IComparer<string>! It makes sense when you think about it: If a comparer can compare any two objects, it can certainly also compare two strings. This property is referred to as contravariance. A generic type can have both in and out modifiers on its type parameters, as is the case with the Func<…> delegate types: public delegate TResult Func<in TArg, out TResult>(TArg arg); Obviously the argument only ever comes in, and the result only ever comes out. Therefore a Func<object,string> can in fact be used as a Func<string,object>. Limitations Variant type parameters can only be declared on interfaces and delegate types, due to a restriction in the CLR. Variance only applies when there is a reference conversion between the type arguments. For instance, an IEnumerable<int> is not an IEnumerable<object> because the conversion from int to object is a boxing conversion, not a reference conversion. Also please note that the CTP does not contain the new versions of the .NET types mentioned above. In order to experiment with variance you have to declare your own variant interfaces and delegate types. COM Example Here is a larger Office automation example that shows many of the new C# features in action. using System; using System.Diagnostics; using System.Linq; using Excel = Microsoft.Office.Interop.Excel; using Word = Microsoft.Office.Interop.Word; class Program { static void Main(string[] args) { var excel = new Excel.Application(); excel.Visible = true; excel.Workbooks.Add(); // optional arguments omitted excel.Cells[1, 1].Value = "Process Name"; // no casts; Value dynamically excel.Cells[1, 2].Value = "Memory Usage"; // accessed var processes = Process.GetProcesses() .OrderByDescending(p =&gt; p.WorkingSet) .Take(10); int i = 2; foreach (var p in processes) { excel.Cells[i, 1].Value = p.ProcessName; // no casts excel.Cells[i, 2].Value = p.WorkingSet; // no casts i++; } Excel.Range range = excel.Cells[1, 1]; // no casts Excel.Chart chart = excel.ActiveWorkbook.Charts. Add(After: excel.ActiveSheet); // named and optional arguments chart.ChartWizard( Source: range.CurrentRegion, Title: "Memory Usage in " + Environment.MachineName); //named+optional chart.ChartStyle = 45; chart.CopyPicture(Excel.XlPictureAppearance.xlScreen, Excel.XlCopyPictureFormat.xlBitmap, Excel.XlPictureAppearance.xlScreen); var word = new Word.Application(); word.Visible = true; word.Documents.Add(); // optional arguments word.Selection.Paste(); } } The code is much more terse and readable than the C# 3.0 counterpart. Note especially how the Value property is accessed dynamically. This is actually an indexed property, i.e. a property that takes an argument; something which C# does not understand. However the argument is optional. Since the access is dynamic, it goes through the runtime COM binder which knows to substitute the default value and call the indexed property. Thus, dynamic COM allows you to avoid accesses to the puzzling Value2 property of Excel ranges. Relationship with Visual Basic A number of the features introduced to C# 4.0 already exist or will be introduced in some form or other in Visual Basic: · Late binding in VB is similar in many ways to dynamic lookup in C#, and can be expected to make more use of the DLR in the future, leading to further parity with C#. · Named and optional arguments have been part of Visual Basic for a long time, and the C# version of the feature is explicitly engineered with maximal VB interoperability in mind. · NoPIA and variance are both being introduced to VB and C# at the same time. VB in turn is adding a number of features that have hitherto been a mainstay of C#. As a result future versions of C# and VB will have much better feature parity, for the benefit of everyone. Resources All available resources concerning C# 4.0 can be accessed through the C# Dev Center. Specifically, this white paper and other resources can be found at the Code Gallery site. Enjoy! span.fullpost {display:none;}

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  • Red Gate Coder interviews: Alex Davies

    - by Michael Williamson
    Alex Davies has been a software engineer at Red Gate since graduating from university, and is currently busy working on .NET Demon. We talked about tackling parallel programming with his actors framework, a scientific approach to debugging, and how JavaScript is going to affect the programming languages we use in years to come. So, if we start at the start, how did you get started in programming? When I was seven or eight, I was given a BBC Micro for Christmas. I had asked for a Game Boy, but my dad thought it would be better to give me a proper computer. For a year or so, I only played games on it, but then I found the user guide for writing programs in it. I gradually started doing more stuff on it and found it fun. I liked creating. As I went into senior school I continued to write stuff on there, trying to write games that weren’t very good. I got a real computer when I was fourteen and found ways to write BASIC on it. Visual Basic to start with, and then something more interesting than that. How did you learn to program? Was there someone helping you out? Absolutely not! I learnt out of a book, or by experimenting. I remember the first time I found a loop, I was like “Oh my God! I don’t have to write out the same line over and over and over again any more. It’s amazing!” When did you think this might be something that you actually wanted to do as a career? For a long time, I thought it wasn’t something that you would do as a career, because it was too much fun to be a career. I thought I’d do chemistry at university and some kind of career based on chemical engineering. And then I went to a careers fair at school when I was seventeen or eighteen, and it just didn’t interest me whatsoever. I thought “I could be a programmer, and there’s loads of money there, and I’m good at it, and it’s fun”, but also that I shouldn’t spoil my hobby. Now I don’t really program in my spare time any more, which is a bit of a shame, but I program all the rest of the time, so I can live with it. Do you think you learnt much about programming at university? Yes, definitely! I went into university knowing how to make computers do anything I wanted them to do. However, I didn’t have the language to talk about algorithms, so the algorithms course in my first year was massively important. Learning other language paradigms like functional programming was really good for breadth of understanding. Functional programming influences normal programming through design rather than actually using it all the time. I draw inspiration from it to write imperative programs which I think is actually becoming really fashionable now, but I’ve been doing it for ages. I did it first! There were also some courses on really odd programming languages, a bit of Prolog, a little bit of C. Having a little bit of each of those is something that I would have never done on my own, so it was important. And then there are knowledge-based courses which are about not programming itself but things that have been programmed like TCP. Those are really important for examples for how to approach things. Did you do any internships while you were at university? Yeah, I spent both of my summers at the same company. I thought I could code well before I went there. Looking back at the crap that I produced, it was only surpassed in its crappiness by all of the other code already in that company. I’m so much better at writing nice code now than I used to be back then. Was there just not a culture of looking after your code? There was, they just didn’t hire people for their abilities in that area. They hired people for raw IQ. The first indicator of it going wrong was that they didn’t have any computer scientists, which is a bit odd in a programming company. But even beyond that they didn’t have people who learnt architecture from anyone else. Most of them had started straight out of university, so never really had experience or mentors to learn from. There wasn’t the experience to draw from to teach each other. In the second half of my second internship, I was being given tasks like looking at new technologies and teaching people stuff. Interns shouldn’t be teaching people how to do their jobs! All interns are going to have little nuggets of things that you don’t know about, but they shouldn’t consistently be the ones who know the most. It’s not a good environment to learn. I was going to ask how you found working with people who were more experienced than you… When I reached Red Gate, I found some people who were more experienced programmers than me, and that was difficult. I’ve been coding since I was tiny. At university there were people who were cleverer than me, but there weren’t very many who were more experienced programmers than me. During my internship, I didn’t find anyone who I classed as being a noticeably more experienced programmer than me. So, it was a shock to the system to have valid criticisms rather than just formatting criticisms. However, Red Gate’s not so big on the actual code review, at least it wasn’t when I started. We did an entire product release and then somebody looked over all of the UI of that product which I’d written and say what they didn’t like. By that point, it was way too late and I’d disagree with them. Do you think the lack of code reviews was a bad thing? I think if there’s going to be any oversight of new people, then it should be continuous rather than chunky. For me I don’t mind too much, I could go out and get oversight if I wanted it, and in those situations I felt comfortable without it. If I was managing the new person, then maybe I’d be keener on oversight and then the right way to do it is continuously and in very, very small chunks. Have you had any significant projects you’ve worked on outside of a job? When I was a teenager I wrote all sorts of stuff. I used to write games, I derived how to do isomorphic projections myself once. I didn’t know what the word was so I couldn’t Google for it, so I worked it out myself. It was horrifically complicated. But it sort of tailed off when I started at university, and is now basically zero. If I do side-projects now, they tend to be work-related side projects like my actors framework, NAct, which I started in a down tools week. Could you explain a little more about NAct? It is a little C# framework for writing parallel code more easily. Parallel programming is difficult when you need to write to shared data. Sometimes parallel programming is easy because you don’t need to write to shared data. When you do need to access shared data, you could just have your threads pile in and do their work, but then you would screw up the data because the threads would trample on each other’s toes. You could lock, but locks are really dangerous if you’re using more than one of them. You get interactions like deadlocks, and that’s just nasty. Actors instead allows you to say this piece of data belongs to this thread of execution, and nobody else can read it. If you want to read it, then ask that thread of execution for a piece of it by sending a message, and it will send the data back by a message. And that avoids deadlocks as long as you follow some obvious rules about not making your actors sit around waiting for other actors to do something. There are lots of ways to write actors, NAct allows you to do it as if it was method calls on other objects, which means you get all the strong type-safety that C# programmers like. Do you think that this is suitable for the majority of parallel programming, or do you think it’s only suitable for specific cases? It’s suitable for most difficult parallel programming. If you’ve just got a hundred web requests which are all independent of each other, then I wouldn’t bother because it’s easier to just spin them up in separate threads and they can proceed independently of each other. But where you’ve got difficult parallel programming, where you’ve got multiple threads accessing multiple bits of data in multiple ways at different times, then actors is at least as good as all other ways, and is, I reckon, easier to think about. When you’re using actors, you presumably still have to write your code in a different way from you would otherwise using single-threaded code. You can’t use actors with any methods that have return types, because you’re not allowed to call into another actor and wait for it. If you want to get a piece of data out of another actor, then you’ve got to use tasks so that you can use “async” and “await” to await asynchronously for it. But other than that, you can still stick things in classes so it’s not too different really. Rather than having thousands of objects with mutable state, you can use component-orientated design, where there are only a few mutable classes which each have a small number of instances. Then there can be thousands of immutable objects. If you tend to do that anyway, then actors isn’t much of a jump. If I’ve already built my system without any parallelism, how hard is it to add actors to exploit all eight cores on my desktop? Usually pretty easy. If you can identify even one boundary where things look like messages and you have components where some objects live on one side and these other objects live on the other side, then you can have a granddaddy object on one side be an actor and it will parallelise as it goes across that boundary. Not too difficult. If we do get 1000-core desktop PCs, do you think actors will scale up? It’s hard. There are always in the order of twenty to fifty actors in my whole program because I tend to write each component as actors, and I tend to have one instance of each component. So this won’t scale to a thousand cores. What you can do is write data structures out of actors. I use dictionaries all over the place, and if you need a dictionary that is going to be accessed concurrently, then you could build one of those out of actors in no time. You can use queuing to marshal requests between different slices of the dictionary which are living on different threads. So it’s like a distributed hash table but all of the chunks of it are on the same machine. That means that each of these thousand processors has cached one small piece of the dictionary. I reckon it wouldn’t be too big a leap to start doing proper parallelism. Do you think it helps if actors get baked into the language, similarly to Erlang? Erlang is excellent in that it has thread-local garbage collection. C# doesn’t, so there’s a limit to how well C# actors can possibly scale because there’s a single garbage collected heap shared between all of them. When you do a global garbage collection, you’ve got to stop all of the actors, which is seriously expensive, whereas in Erlang garbage collections happen per-actor, so they’re insanely cheap. However, Erlang deviated from all the sensible language design that people have used recently and has just come up with crazy stuff. You can definitely retrofit thread-local garbage collection to .NET, and then it’s quite well-suited to support actors, even if it’s not baked into the language. Speaking of language design, do you have a favourite programming language? I’ll choose a language which I’ve never written before. I like the idea of Scala. It sounds like C#, only with some of the niggles gone. I enjoy writing static types. It means you don’t have to writing tests so much. When you say it doesn’t have some of the niggles? C# doesn’t allow the use of a property as a method group. It doesn’t have Scala case classes, or sum types, where you can do a switch statement and the compiler checks that you’ve checked all the cases, which is really useful in functional-style programming. Pattern-matching, in other words. That’s actually the major niggle. C# is pretty good, and I’m quite happy with C#. And what about going even further with the type system to remove the need for tests to something like Haskell? Or is that a step too far? I’m quite a pragmatist, I don’t think I could deal with trying to write big systems in languages with too few other users, especially when learning how to structure things. I just don’t know anyone who can teach me, and the Internet won’t teach me. That’s the main reason I wouldn’t use it. If I turned up at a company that writes big systems in Haskell, I would have no objection to that, but I wouldn’t instigate it. What about things in C#? For instance, there’s contracts in C#, so you can try to statically verify a bit more about your code. Do you think that’s useful, or just not worthwhile? I’ve not really tried it. My hunch is that it needs to be built into the language and be quite mathematical for it to work in real life, and that doesn’t seem to have ended up true for C# contracts. I don’t think anyone who’s tried them thinks they’re any good. I might be wrong. On a slightly different note, how do you like to debug code? I think I’m quite an odd debugger. I use guesswork extremely rarely, especially if something seems quite difficult to debug. I’ve been bitten spending hours and hours on guesswork and not being scientific about debugging in the past, so now I’m scientific to a fault. What I want is to see the bug happening in the debugger, to step through the bug happening. To watch the program going from a valid state to an invalid state. When there’s a bug and I can’t work out why it’s happening, I try to find some piece of evidence which places the bug in one section of the code. From that experiment, I binary chop on the possible causes of the bug. I suppose that means binary chopping on places in the code, or binary chopping on a stage through a processing cycle. Basically, I’m very stupid about how I debug. I won’t make any guesses, I won’t use any intuition, I will only identify the experiment that’s going to binary chop most effectively and repeat rather than trying to guess anything. I suppose it’s quite top-down. Is most of the time then spent in the debugger? Absolutely, if at all possible I will never debug using print statements or logs. I don’t really hold much stock in outputting logs. If there’s any bug which can be reproduced locally, I’d rather do it in the debugger than outputting logs. And with SmartAssembly error reporting, there’s not a lot that can’t be either observed in an error report and just fixed, or reproduced locally. And in those other situations, maybe I’ll use logs. But I hate using logs. You stare at the log, trying to guess what’s going on, and that’s exactly what I don’t like doing. You have to just look at it and see does this look right or wrong. We’ve covered how you get to grip with bugs. How do you get to grips with an entire codebase? I watch it in the debugger. I find little bugs and then try to fix them, and mostly do it by watching them in the debugger and gradually getting an understanding of how the code works using my process of binary chopping. I have to do a lot of reading and watching code to choose where my slicing-in-half experiment is going to be. The last time I did it was SmartAssembly. The old code was a complete mess, but at least it did things top to bottom. There wasn’t too much of some of the big abstractions where flow of control goes all over the place, into a base class and back again. Code’s really hard to understand when that happens. So I like to choose a little bug and try to fix it, and choose a bigger bug and try to fix it. Definitely learn by doing. I want to always have an aim so that I get a little achievement after every few hours of debugging. Once I’ve learnt the codebase I might be able to fix all the bugs in an hour, but I’d rather be using them as an aim while I’m learning the codebase. If I was a maintainer of a codebase, what should I do to make it as easy as possible for you to understand? Keep distinct concepts in different places. And name your stuff so that it’s obvious which concepts live there. You shouldn’t have some variable that gets set miles up the top of somewhere, and then is read miles down to choose some later behaviour. I’m talking from a very much SmartAssembly point of view because the old SmartAssembly codebase had tons and tons of these things, where it would read some property of the code and then deal with it later. Just thousands of variables in scope. Loads of things to think about. If you can keep concepts separate, then it aids me in my process of fixing bugs one at a time, because each bug is going to more or less be understandable in the one place where it is. And what about tests? Do you think they help at all? I’ve never had the opportunity to learn a codebase which has had tests, I don’t know what it’s like! What about when you’re actually developing? How useful do you find tests in finding bugs or regressions? Finding regressions, absolutely. Running bits of code that would be quite hard to run otherwise, definitely. It doesn’t happen very often that a test finds a bug in the first place. I don’t really buy nebulous promises like tests being a good way to think about the spec of the code. My thinking goes something like “This code works at the moment, great, ship it! Ah, there’s a way that this code doesn’t work. Okay, write a test, demonstrate that it doesn’t work, fix it, use the test to demonstrate that it’s now fixed, and keep the test for future regressions.” The most valuable tests are for bugs that have actually happened at some point, because bugs that have actually happened at some point, despite the fact that you think you’ve fixed them, are way more likely to appear again than new bugs are. Does that mean that when you write your code the first time, there are no tests? Often. The chance of there being a bug in a new feature is relatively unaffected by whether I’ve written a test for that new feature because I’m not good enough at writing tests to think of bugs that I would have written into the code. So not writing regression tests for all of your code hasn’t affected you too badly? There are different kinds of features. Some of them just always work, and are just not flaky, they just continue working whatever you throw at them. Maybe because the type-checker is particularly effective around them. Writing tests for those features which just tend to always work is a waste of time. And because it’s a waste of time I’ll tend to wait until a feature has demonstrated its flakiness by having bugs in it before I start trying to test it. You can get a feel for whether it’s going to be flaky code as you’re writing it. I try to write it to make it not flaky, but there are some things that are just inherently flaky. And very occasionally, I’ll think “this is going to be flaky” as I’m writing, and then maybe do a test, but not most of the time. How do you think your programming style has changed over time? I’ve got clearer about what the right way of doing things is. I used to flip-flop a lot between different ideas. Five years ago I came up with some really good ideas and some really terrible ideas. All of them seemed great when I thought of them, but they were quite diverse ideas, whereas now I have a smaller set of reliable ideas that are actually good for structuring code. So my code is probably more similar to itself than it used to be back in the day, when I was trying stuff out. I’ve got more disciplined about encapsulation, I think. There are operational things like I use actors more now than I used to, and that forces me to use immutability more than I used to. The first code that I wrote in Red Gate was the memory profiler UI, and that was an actor, I just didn’t know the name of it at the time. I don’t really use object-orientation. By object-orientation, I mean having n objects of the same type which are mutable. I want a constant number of objects that are mutable, and they should be different types. I stick stuff in dictionaries and then have one thing that owns the dictionary and puts stuff in and out of it. That’s definitely a pattern that I’ve seen recently. I think maybe I’m doing functional programming. Possibly. It’s plausible. If you had to summarise the essence of programming in a pithy sentence, how would you do it? Programming is the form of art that, without losing any of the beauty of architecture or fine art, allows you to produce things that people love and you make money from. So you think it’s an art rather than a science? It’s a little bit of engineering, a smidgeon of maths, but it’s not science. Like architecture, programming is on that boundary between art and engineering. If you want to do it really nicely, it’s mostly art. You can get away with doing architecture and programming entirely by having a good engineering mind, but you’re not going to produce anything nice. You’re not going to have joy doing it if you’re an engineering mind. Architects who are just engineering minds are not going to enjoy their job. I suppose engineering is the foundation on which you build the art. Exactly. How do you think programming is going to change over the next ten years? There will be an unfortunate shift towards dynamically-typed languages, because of JavaScript. JavaScript has an unfair advantage. JavaScript’s unfair advantage will cause more people to be exposed to dynamically-typed languages, which means other dynamically-typed languages crop up and the best features go into dynamically-typed languages. Then people conflate the good features with the fact that it’s dynamically-typed, and more investment goes into dynamically-typed languages. They end up better, so people use them. What about the idea of compiling other languages, possibly statically-typed, to JavaScript? It’s a reasonable idea. I would like to do it, but I don’t think enough people in the world are going to do it to make it pick up. The hordes of beginners are the lifeblood of a language community. They are what makes there be good tools and what makes there be vibrant community websites. And any particular thing which is the same as JavaScript only with extra stuff added to it, although it might be technically great, is not going to have the hordes of beginners. JavaScript is always to be quickest and easiest way for a beginner to start programming in the browser. And dynamically-typed languages are great for beginners. Compilers are pretty scary and beginners don’t write big code. And having your errors come up in the same place, whether they’re statically checkable errors or not, is quite nice for a beginner. If someone asked me to teach them some programming, I’d teach them JavaScript. If dynamically-typed languages are great for beginners, when do you think the benefits of static typing start to kick in? The value of having a statically typed program is in the tools that rely on the static types to produce a smooth IDE experience rather than actually telling me my compile errors. And only once you’re experienced enough a programmer that having a really smooth IDE experience makes a blind bit of difference, does static typing make a blind bit of difference. So it’s not really about size of codebase. If I go and write up a tiny program, I’m still going to get value out of writing it in C# using ReSharper because I’m experienced with C# and ReSharper enough to be able to write code five times faster if I have that help. Any other visions of the future? Nobody’s going to use actors. Because everyone’s going to be running on single-core VMs connected over network-ready protocols like JSON over HTTP. So, parallelism within one operating system is going to die. But until then, you should use actors. More Red Gater Coder interviews

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  • Using HTML 5 SessionState to save rendered Page Content

    - by Rick Strahl
    HTML 5 SessionState and LocalStorage are very useful and super easy to use to manage client side state. For building rich client side or SPA style applications it's a vital feature to be able to cache user data as well as HTML content in order to swap pages in and out of the browser's DOM. What might not be so obvious is that you can also use the sessionState and localStorage objects even in classic server rendered HTML applications to provide caching features between pages. These APIs have been around for a long time and are supported by most relatively modern browsers and even all the way back to IE8, so you can use them safely in your Web applications. SessionState and LocalStorage are easy The APIs that make up sessionState and localStorage are very simple. Both object feature the same API interface which  is a simple, string based key value store that has getItem, setItem, removeitem, clear and  key methods. The objects are also pseudo array objects and so can be iterated like an array with  a length property and you have array indexers to set and get values with. Basic usage  for storing and retrieval looks like this (using sessionStorage, but the syntax is the same for localStorage - just switch the objects):// set var lastAccess = new Date().getTime(); if (sessionStorage) sessionStorage.setItem("myapp_time", lastAccess.toString()); // retrieve in another page or on a refresh var time = null; if (sessionStorage) time = sessionStorage.getItem("myapp_time"); if (time) time = new Date(time * 1); else time = new Date(); sessionState stores data that is browser session specific and that has a liftetime of the active browser session or window. Shut down the browser or tab and the storage goes away. localStorage uses the same API interface, but the lifetime of the data is permanently stored in the browsers storage area until deleted via code or by clearing out browser cookies (not the cache). Both sessionStorage and localStorage space is limited. The spec is ambiguous about this - supposedly sessionStorage should allow for unlimited size, but it appears that most WebKit browsers support only 2.5mb for either object. This means you have to be careful what you store especially since other applications might be running on the same domain and also use the storage mechanisms. That said 2.5mb worth of character data is quite a bit and would go a long way. The easiest way to get a feel for how sessionState and localStorage work is to look at a simple example. You can go check out the following example online in Plunker: http://plnkr.co/edit/0ICotzkoPjHaWa70GlRZ?p=preview which looks like this: Plunker is an online HTML/JavaScript editor that lets you write and run Javascript code and similar to JsFiddle, but a bit cleaner to work in IMHO (thanks to John Papa for turning me on to it). The sample has two text boxes with counts that update session/local storage every time you click the related button. The counts are 'cached' in Session and Local storage. The point of these examples is that both counters survive full page reloads, and the LocalStorage counter survives a complete browser shutdown and restart. Go ahead and try it out by clicking the Reload button after updating both counters and then shutting down the browser completely and going back to the same URL (with the same browser). What you should see is that reloads leave both counters intact at the counted values, while a browser restart will leave only the local storage counter intact. The code to deal with the SessionStorage (and LocalStorage not shown here) in the example is isolated into a couple of wrapper methods to simplify the code: function getSessionCount() { var count = 0; if (sessionStorage) { var count = sessionStorage.getItem("ss_count"); count = !count ? 0 : count * 1; } $("#txtSession").val(count); return count; } function setSessionCount(count) { if (sessionStorage) sessionStorage.setItem("ss_count", count.toString()); } These two functions essentially load and store a session counter value. The two key methods used here are: sessionStorage.getItem(key); sessionStorage.setItem(key,stringVal); Note that the value given to setItem and return by getItem has to be a string. If you pass another type you get an error. Don't let that limit you though - you can easily enough store JSON data in a variable so it's quite possible to pass complex objects and store them into a single sessionStorage value:var user = { name: "Rick", id="ricks", level=8 } sessionStorage.setItem("app_user",JSON.stringify(user)); to retrieve it:var user = sessionStorage.getItem("app_user"); if (user) user = JSON.parse(user); Simple! If you're using the Chrome Developer Tools (F12) you can also check out the session and local storage state on the Resource tab:   You can also use this tool to refresh or remove entries from storage. What we just looked at is a purely client side implementation where a couple of counters are stored. For rich client centric AJAX applications sessionStorage and localStorage provide a very nice and simple API to store application state while the application is running. But you can also use these storage mechanisms to manage server centric HTML applications when you combine server rendering with some JavaScript to perform client side data caching. You can both store some state information and data on the client (ie. store a JSON object and carry it forth between server rendered HTML requests) or you can use it for good old HTTP based caching where some rendered HTML is saved and then restored later. Let's look at the latter with a real life example. Why do I need Client-side Page Caching for Server Rendered HTML? I don't know about you, but in a lot of my existing server driven applications I have lists that display a fair amount of data. Typically these lists contain links to then drill down into more specific data either for viewing or editing. You can then click on a link and go off to a detail page that provides more concise content. So far so good. But now you're done with the detail page and need to get back to the list, so you click on a 'bread crumbs trail' or an application level 'back to list' button and… …you end up back at the top of the list - the scroll position, the current selection in some cases even filters conditions - all gone with the wind. You've left behind the state of the list and are starting from scratch in your browsing of the list from the top. Not cool! Sound familiar? This a pretty common scenario with server rendered HTML content where it's so common to display lists to drill into, only to lose state in the process of returning back to the original list. Look at just about any traditional forums application, or even StackOverFlow to see what I mean here. Scroll down a bit to look at a post or entry, drill in then use the bread crumbs or tab to go back… In some cases returning to the top of a list is not a big deal. On StackOverFlow that sort of works because content is turning around so quickly you probably want to actually look at the top posts. Not always though - if you're browsing through a list of search topics you're interested in and drill in there's no way back to that position. Essentially anytime you're actively browsing the items in the list, that's when state becomes important and if it's not handled the user experience can be really disrupting. Content Caching If you're building client centric SPA style applications this is a fairly easy to solve problem - you tend to render the list once and then update the page content to overlay the detail content, only hiding the list temporarily until it's used again later. It's relatively easy to accomplish this simply by hiding content on the page and later making it visible again. But if you use server rendered content, hanging on to all the detail like filters, selections and scroll position is not quite as easy. Or is it??? This is where sessionStorage comes in handy. What if we just save the rendered content of a previous page, and then restore it when we return to this page based on a special flag that tells us to use the cached version? Let's see how we can do this. A real World Use Case Recently my local ISP asked me to help out with updating an ancient classifieds application. They had a very busy, local classifieds app that was originally an ASP classic application. The old app was - wait for it: frames based - and even though I lobbied against it, the decision was made to keep the frames based layout to allow rapid browsing of the hundreds of posts that are made on a daily basis. The primary reason they wanted this was precisely for the ability to quickly browse content item by item. While I personally hate working with Frames, I have to admit that the UI actually works well with the frames layout as long as you're running on a large desktop screen. You can check out the frames based desktop site here: http://classifieds.gorge.net/ However when I rebuilt the app I also added a secondary view that doesn't use frames. The main reason for this of course was for mobile displays which work horribly with frames. So there's a somewhat mobile friendly interface to the interface, which ditches the frames and uses some responsive design tweaking for mobile capable operation: http://classifeds.gorge.net/mobile  (or browse the base url with your browser width under 800px)   Here's what the mobile, non-frames view looks like:   As you can see this means that the list of classifieds posts now is a list and there's a separate page for drilling down into the item. And of course… originally we ran into that usability issue I mentioned earlier where the browse, view detail, go back to the list cycle resulted in lost list state. Originally in mobile mode you scrolled through the list, found an item to look at and drilled in to display the item detail. Then you clicked back to the list and BAM - you've lost your place. Because there are so many items added on a daily basis the full list is never fully loaded, but rather there's a "Load Additional Listings"  entry at the button. Not only did we originally lose our place when coming back to the list, but any 'additionally loaded' items are no longer there because the list was now rendering  as if it was the first page hit. The additional listings, and any filters, the selection of an item all were lost. Major Suckage! Using Client SessionStorage to cache Server Rendered Content To work around this problem I decided to cache the rendered page content from the list in SessionStorage. Anytime the list renders or is updated with Load Additional Listings, the page HTML is cached and stored in Session Storage. Any back links from the detail page or the login or write entry forms then point back to the list page with a back=true query string parameter. If the server side sees this parameter it doesn't render the part of the page that is cached. Instead the client side code retrieves the data from the sessionState cache and simply inserts it into the page. It sounds pretty simple, and the overall the process is really easy, but there are a few gotchas that I'll discuss in a minute. But first let's look at the implementation. Let's start with the server side here because that'll give a quick idea of the doc structure. As I mentioned the server renders data from an ASP.NET MVC view. On the list page when returning to the list page from the display page (or a host of other pages) looks like this: https://classifieds.gorge.net/list?back=True The query string value is a flag, that indicates whether the server should render the HTML. Here's what the top level MVC Razor view for the list page looks like:@model MessageListViewModel @{ ViewBag.Title = "Classified Listing"; bool isBack = !string.IsNullOrEmpty(Request.QueryString["back"]); } <form method="post" action="@Url.Action("list")"> <div id="SizingContainer"> @if (!isBack) { @Html.Partial("List_CommandBar_Partial", Model) <div id="PostItemContainer" class="scrollbox" xstyle="-webkit-overflow-scrolling: touch;"> @Html.Partial("List_Items_Partial", Model) @if (Model.RequireLoadEntry) { <div class="postitem loadpostitems" style="padding: 15px;"> <div id="LoadProgress" class="smallprogressright"></div> <div class="control-progress"> Load additional listings... </div> </div> } </div> } </div> </form> As you can see the query string triggers a conditional block that if set is simply not rendered. The content inside of #SizingContainer basically holds  the entire page's HTML sans the headers and scripts, but including the filter options and menu at the top. In this case this makes good sense - in other situations the fact that the menu or filter options might be dynamically updated might make you only cache the list rather than essentially the entire page. In this particular instance all of the content works and produces the proper result as both the list along with any filter conditions in the form inputs are restored. Ok, let's move on to the client. On the client there are two page level functions that deal with saving and restoring state. Like the counter example I showed earlier, I like to wrap the logic to save and restore values from sessionState into a separate function because they are almost always used in several places.page.saveData = function(id) { if (!sessionStorage) return; var data = { id: id, scroll: $("#PostItemContainer").scrollTop(), html: $("#SizingContainer").html() }; sessionStorage.setItem("list_html",JSON.stringify(data)); }; page.restoreData = function() { if (!sessionStorage) return; var data = sessionStorage.getItem("list_html"); if (!data) return null; return JSON.parse(data); }; The data that is saved is an object which contains an ID which is the selected element when the user clicks and a scroll position. These two values are used to reset the scroll position when the data is used from the cache. Finally the html from the #SizingContainer element is stored, which makes for the bulk of the document's HTML. In this application the HTML captured could be a substantial bit of data. If you recall, I mentioned that the server side code renders a small chunk of data initially and then gets more data if the user reads through the first 50 or so items. The rest of the items retrieved can be rather sizable. Other than the JSON deserialization that's Ok. Since I'm using SessionStorage the storage space has no immediate limits. Next is the core logic to handle saving and restoring the page state. At first though this would seem pretty simple, and in some cases it might be, but as the following code demonstrates there are a few gotchas to watch out for. Here's the relevant code I use to save and restore:$( function() { … var isBack = getUrlEncodedKey("back", location.href); if (isBack) { // remove the back key from URL setUrlEncodedKey("back", "", location.href); var data = page.restoreData(); // restore from sessionState if (!data) { // no data - force redisplay of the server side default list window.location = "list"; return; } $("#SizingContainer").html(data.html); var el = $(".postitem[data-id=" + data.id + "]"); $(".postitem").removeClass("highlight"); el.addClass("highlight"); $("#PostItemContainer").scrollTop(data.scroll); setTimeout(function() { el.removeClass("highlight"); }, 2500); } else if (window.noFrames) page.saveData(null); // save when page loads $("#SizingContainer").on("click", ".postitem", function() { var id = $(this).attr("data-id"); if (!id) return true; if (window.noFrames) page.saveData(id); var contentFrame = window.parent.frames["Content"]; if (contentFrame) contentFrame.location.href = "show/" + id; else window.location.href = "show/" + id; return false; }); … The code starts out by checking for the back query string flag which triggers restoring from the client cache. If cached the cached data structure is read from sessionStorage. It's important here to check if data was returned. If the user had back=true on the querystring but there is no cached data, he likely bookmarked this page or otherwise shut down the browser and came back to this URL. In that case the server didn't render any detail and we have no cached data, so all we can do is redirect to the original default list view using window.location. If we continued the page would render no data - so make sure to always check the cache retrieval result. Always! If there is data the it's loaded and the data.html data is restored back into the document by simply injecting the HTML back into the document's #SizingContainer element:$("#SizingContainer").html(data.html); It's that simple and it's quite quick even with a fully loaded list of additional items and on a phone. The actual HTML data is stored to the cache on every page load initially and then again when the user clicks on an element to navigate to a particular listing. The former ensures that the client cache always has something in it, and the latter updates with additional information for the selected element. For the click handling I use a data-id attribute on the list item (.postitem) in the list and retrieve the id from that. That id is then used to navigate to the actual entry as well as storing that Id value in the saved cached data. The id is used to reset the selection by searching for the data-id value in the restored elements. The overall process of this save/restore process is pretty straight forward and it doesn't require a bunch of code, yet it yields a huge improvement in the usability of the site on mobile devices (or anybody who uses the non-frames view). Some things to watch out for As easy as it conceptually seems to simply store and retrieve cached content, you have to be quite aware what type of content you are caching. The code above is all that's specific to cache/restore cycle and it works, but it took a few tweaks to the rest of the script code and server code to make it all work. There were a few gotchas that weren't immediately obvious. Here are a few things to pay attention to: Event Handling Logic Timing of manipulating DOM events Inline Script Code Bookmarking to the Cache Url when no cache exists Do you have inline script code in your HTML? That script code isn't going to run if you restore from cache and simply assign or it may not run at the time you think it would normally in the DOM rendering cycle. JavaScript Event Hookups The biggest issue I ran into with this approach almost immediately is that originally I had various static event handlers hooked up to various UI elements that are now cached. If you have an event handler like:$("#btnSearch").click( function() {…}); that works fine when the page loads with server rendered HTML, but that code breaks when you now load the HTML from cache. Why? Because the elements you're trying to hook those events to may not actually be there - yet. Luckily there's an easy workaround for this by using deferred events. With jQuery you can use the .on() event handler instead:$("#SelectionContainer").on("click","#btnSearch", function() {…}); which monitors a parent element for the events and checks for the inner selector elements to handle events on. This effectively defers to runtime event binding, so as more items are added to the document bindings still work. For any cached content use deferred events. Timing of manipulating DOM Elements Along the same lines make sure that your DOM manipulation code follows the code that loads the cached content into the page so that you don't manipulate DOM elements that don't exist just yet. Ideally you'll want to check for the condition to restore cached content towards the top of your script code, but that can be tricky if you have components or other logic that might not all run in a straight line. Inline Script Code Here's another small problem I ran into: I use a DateTime Picker widget I built a while back that relies on the jQuery date time picker. I also created a helper function that allows keyboard date navigation into it that uses JavaScript logic. Because MVC's limited 'object model' the only way to embed widget content into the page is through inline script. This code broken when I inserted the cached HTML into the page because the script code was not available when the component actually got injected into the page. As the last bullet - it's a matter of timing. There's no good work around for this - in my case I pulled out the jQuery date picker and relied on native <input type="date" /> logic instead - a better choice these days anyway, especially since this view is meant to be primarily to serve mobile devices which actually support date input through the browser (unlike desktop browsers of which only WebKit seems to support it). Bookmarking Cached Urls When you cache HTML content you have to make a decision whether you cache on the client and also not render that same content on the server. In the Classifieds app I didn't render server side content so if the user comes to the page with back=True and there is no cached content I have to a have a Plan B. Typically this happens when somebody ends up bookmarking the back URL. The easiest and safest solution for this scenario is to ALWAYS check the cache result to make sure it exists and if not have a safe URL to go back to - in this case to the plain uncached list URL which amounts to effectively redirecting. This seems really obvious in hindsight, but it's easy to overlook and not see a problem until much later, when it's not obvious at all why the page is not rendering anything. Don't use <body> to replace Content Since we're practically replacing all the HTML in the page it may seem tempting to simply replace the HTML content of the <body> tag. Don't. The body tag usually contains key things that should stay in the page and be there when it loads. Specifically script tags and elements and possibly other embedded content. It's best to create a top level DOM element specifically as a placeholder container for your cached content and wrap just around the actual content you want to replace. In the app above the #SizingContainer is that container. Other Approaches The approach I've used for this application is kind of specific to the existing server rendered application we're running and so it's just one approach you can take with caching. However for server rendered content caching this is a pattern I've used in a few apps to retrofit some client caching into list displays. In this application I took the path of least resistance to the existing server rendering logic. Here are a few other ways that come to mind: Using Partial HTML Rendering via AJAXInstead of rendering the page initially on the server, the page would load empty and the client would render the UI by retrieving the respective HTML and embedding it into the page from a Partial View. This effectively makes the initial rendering and the cached rendering logic identical and removes the server having to decide whether this request needs to be rendered or not (ie. not checking for a back=true switch). All the logic related to caching is made on the client in this case. Using JSON Data and Client RenderingThe hardcore client option is to do the whole UI SPA style and pull data from the server and then use client rendering or databinding to pull the data down and render using templates or client side databinding with knockout/angular et al. As with the Partial Rendering approach the advantage is that there's no difference in the logic between pulling the data from cache or rendering from scratch other than the initial check for the cache request. Of course if the app is a  full on SPA app, then caching may not be required even - the list could just stay in memory and be hidden and reactivated. I'm sure there are a number of other ways this can be handled as well especially using  AJAX. AJAX rendering might simplify the logic, but it also complicates search engine optimization since there's no content loaded initially. So there are always tradeoffs and it's important to look at all angles before deciding on any sort of caching solution in general. State of the Session SessionState and LocalStorage are easy to use in client code and can be integrated even with server centric applications to provide nice caching features of content and data. In this post I've shown a very specific scenario of storing HTML content for the purpose of remembering list view data and state and making the browsing experience for lists a bit more friendly, especially if there's dynamically loaded content involved. If you haven't played with sessionStorage or localStorage I encourage you to give it a try. There's a lot of cool stuff that you can do with this beyond the specific scenario I've covered here… Resources Overview of localStorage (also applies to sessionStorage) Web Storage Compatibility Modernizr Test Suite© Rick Strahl, West Wind Technologies, 2005-2013Posted in JavaScript  HTML5  ASP.NET  MVC   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • how to make a function recursive

    - by tom smith
    i have this huge function and i am wondering how to make it recursive. i have the base case which should never come true, so it should always go to else and keep calling itself with the variable t increases. any help would be great thanks def draw(x, y, t, planets): if 'Satellites' in planets["Moon"]: print ("fillcircle", x, y, planets["Moon"]['Radius']*scale) else: while True: print("refresh") print("colour 0 0 0") print("clear") print("colour 255 255 255") print("fillcircle",x,y,planets['Sun']['Radius']*scale) print("text ", "\"Sun\"",x+planets['Sun']['Radius']*scale,y) if "Mercury" in planets: r_Mercury=planets['Mercury']['Orbital Radius']*scale; print("circle",x,y,r_Mercury) r_Xmer=x+math.sin(t*2*math.pi/planets['Mercury']['Period'])*r_Mercury r_Ymer=y+math.cos(t*2*math.pi/planets['Mercury']['Period'])*r_Mercury print("fillcircle",r_Xmer,r_Ymer,3) print("text ", "\"Mercury\"",r_Xmer+planets['Mercury']['Radius']*scale,r_Ymer) if "Venus" in planets: r_Venus=planets['Venus']['Orbital Radius']*scale; print("circle",x,y,r_Venus) r_Xven=x+math.sin(t*2*math.pi/planets['Venus']['Period'])*r_Venus r_Yven=y+math.cos(t*2*math.pi/planets['Venus']['Period'])*r_Venus print("fillcircle",r_Xven,r_Yven,3) print("text ", "\"Venus\"",r_Xven+planets['Venus']['Radius']*scale,r_Yven) if "Earth" in planets: r_Earth=planets['Earth']['Orbital Radius']*scale; print("circle",x,y,r_Earth) r_Xe=x+math.sin(t*2*math.pi/planets['Earth']['Period'])*r_Earth r_Ye=y+math.cos(t*2*math.pi/planets['Earth']['Period'])*r_Earth print("fillcircle",r_Xe,r_Ye,3) print("text ", "\"Earth\"",r_Xe+planets['Earth']['Radius']*scale,r_Ye) if "Moon" in planets: r_Moon=planets['Moon']['Orbital Radius']*scale; print("circle",r_Xe,r_Ye,r_Moon) r_Xm=r_Xe+math.sin(t*2*math.pi/planets['Moon']['Period'])*r_Moon r_Ym=r_Ye+math.cos(t*2*math.pi/planets['Moon']['Period'])*r_Moon print("fillcircle",r_Xm,r_Ym,3) print("text ", "\"Moon\"",r_Xm+planets['Moon']['Radius']*scale,r_Ym) if "Mars" in planets: r_Mars=planets['Mars']['Orbital Radius']*scale; print("circle",x,y,r_Mars) r_Xmar=x+math.sin(t*2*math.pi/planets['Mars']['Period'])*r_Mars r_Ymar=y+math.cos(t*2*math.pi/planets['Mars']['Period'])*r_Mars print("fillcircle",r_Xmar,r_Ymar,3) print("text ", "\"Mars\"",r_Xmar+planets['Mars']['Radius']*scale,r_Ymar) if "Phobos" in planets: r_Phobos=planets['Phobos']['Orbital Radius']*scale; print("circle",r_Xmar,r_Ymar,r_Phobos) r_Xpho=r_Xmar+math.sin(t*2*math.pi/planets['Phobos']['Period'])*r_Phobos r_Ypho=r_Ymar+math.cos(t*2*math.pi/planets['Phobos']['Period'])*r_Phobos print("fillcircle",r_Xpho,r_Ypho,3) print("text ", "\"Phobos\"",r_Xpho+planets['Phobos']['Radius']*scale,r_Ypho) if "Deimos" in planets: r_Deimos=planets['Deimos']['Orbital Radius']*scale; print("circle",r_Xmar,r_Ymar,r_Deimos) r_Xdei=r_Xmar+math.sin(t*2*math.pi/planets['Deimos']['Period'])*r_Deimos r_Ydei=r_Ymar+math.cos(t*2*math.pi/planets['Deimos']['Period'])*r_Deimos print("fillcircle",r_Xdei,r_Ydei,3) print("text ", "\"Deimos\"",r_Xpho+planets['Deimos']['Radius']*scale,r_Ydei) if "Ceres" in planets: r_Ceres=planets['Ceres']['Orbital Radius']*scale; print("circle",x,y,r_Ceres) r_Xcer=x+math.sin(t*2*math.pi/planets['Ceres']['Period'])*r_Ceres r_Ycer=y+math.cos(t*2*math.pi/planets['Ceres']['Period'])*r_Ceres print("fillcircle",r_Xcer,r_Ycer,3) print("text ", "\"Ceres\"",r_Xcer+planets['Ceres']['Radius']*scale,r_Ycer) if "Jupiter" in planets: r_Jupiter=planets['Jupiter']['Orbital Radius']*scale; print("circle",x,y,r_Jupiter) r_Xjup=x+math.sin(t*2*math.pi/planets['Jupiter']['Period'])*r_Jupiter r_Yjup=y+math.cos(t*2*math.pi/planets['Jupiter']['Period'])*r_Jupiter print("fillcircle",r_Xjup,r_Yjup,3) print("text ", "\"Jupiter\"",r_Xjup+planets['Jupiter']['Radius']*scale,r_Yjup) if "Io" in planets: r_Io=planets['Io']['Orbital Radius']*scale; print("circle",r_Xjup,r_Yjup,r_Io) r_Xio=r_Xjup+math.sin(t*2*math.pi/planets['Io']['Period'])*r_Io r_Yio=r_Yjup+math.cos(t*2*math.pi/planets['Io']['Period'])*r_Io print("fillcircle",r_Xio,r_Yio,3) print("text ", "\"Io\"",r_Xio+planets['Io']['Radius']*scale,r_Yio) if "Europa" in planets: r_Europa=planets['Europa']['Orbital Radius']*scale; print("circle",r_Xjup,r_Yjup,r_Europa) r_Xeur=r_Xjup+math.sin(t*2*math.pi/planets['Europa']['Period'])*r_Europa r_Yeur=r_Yjup+math.cos(t*2*math.pi/planets['Europa']['Period'])*r_Europa print("fillcircle",r_Xeur,r_Yeur,3) print("text ", "\"Europa\"",r_Xeur+planets['Europa']['Radius']*scale,r_Yeur) if "Ganymede" in planets: r_Ganymede=planets['Ganymede']['Orbital Radius']*scale; print("circle",r_Xjup,r_Yjup,r_Ganymede) r_Xgan=r_Xjup+math.sin(t*2*math.pi/planets['Ganymede']['Period'])*r_Ganymede r_Ygan=r_Yjup+math.cos(t*2*math.pi/planets['Ganymede']['Period'])*r_Ganymede print("fillcircle",r_Xgan,r_Ygan,3) print("text ", "\"Ganymede\"",r_Xgan+planets['Ganymede']['Radius']*scale,r_Ygan) if "Callisto" in planets: r_Callisto=planets['Callisto']['Orbital Radius']*scale; print("circle",r_Xjup,r_Yjup,r_Callisto) r_Xcal=r_Xjup+math.sin(t*2*math.pi/planets['Callisto']['Period'])*r_Callisto r_Ycal=r_Yjup+math.cos(t*2*math.pi/planets['Callisto']['Period'])*r_Callisto print("fillcircle",r_Xcal,r_Ycal,3) print("text ", "\"Callisto\"",r_Xcal+planets['Callisto']['Radius']*scale,r_Ycal) if "Saturn" in planets: r_Saturn=planets['Saturn']['Orbital Radius']*scale; print("circle",x,y,r_Saturn) r_Xsat=x+math.sin(t*2*math.pi/planets['Saturn']['Period'])*r_Saturn r_Ysat=y+math.cos(t*2*math.pi/planets['Saturn']['Period'])*r_Saturn print("fillcircle",r_Xsat,r_Ysat,3) print("text ", "\"Saturn\"",r_Xsat+planets['Saturn']['Radius']*scale,r_Ysat) if "Mimas" in planets: r_Mimas=planets['Mimas']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Mimas) r_Xmim=r_Xsat+math.sin(t*2*math.pi/planets['Mimas']['Period'])*r_Mimas r_Ymim=r_Ysat+math.cos(t*2*math.pi/planets['Mimas']['Period'])*r_Mimas print("fillcircle",r_Xmim,r_Ymim,3) print("text ", "\"Mimas\"",r_Xmim+planets['Mimas']['Radius']*scale,r_Ymim) if "Enceladus" in planets: r_Enceladus=planets['Enceladus']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Enceladus) r_Xenc=r_Xsat+math.sin(t*2*math.pi/planets['Enceladus']['Period'])*r_Enceladus r_Yenc=r_Ysat+math.cos(t*2*math.pi/planets['Enceladus']['Period'])*r_Enceladus print("fillcircle",r_Xenc,r_Yenc,3) print("text ", "\"Enceladus\"",r_Xenc+planets['Enceladus']['Radius']*scale,r_Yenc) if "Tethys" in planets: r_Tethys=planets['Tethys']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Tethys) r_Xtet=r_Xsat+math.sin(t*2*math.pi/planets['Tethys']['Period'])*r_Tethys r_Ytet=r_Ysat+math.cos(t*2*math.pi/planets['Tethys']['Period'])*r_Tethys print("fillcircle",r_Xtet,r_Ytet,3) print("text ", "\"Tethys\"",r_Xtet+planets['Tethys']['Radius']*scale,r_Ytet) if "Dione" in planets: r_Dione=planets['Dione']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Dione) r_Xdio=r_Xsat+math.sin(t*2*math.pi/planets['Dione']['Period'])*r_Dione r_Ydio=r_Ysat+math.cos(t*2*math.pi/planets['Dione']['Period'])*r_Dione print("fillcircle",r_Xdio,r_Ydio,3) print("text ", "\"Dione\"",r_Xdio+planets['Dione']['Radius']*scale,r_Ydio) if "Rhea" in planets: r_Rhea=planets['Rhea']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Rhea) r_Xrhe=r_Xsat+math.sin(t*2*math.pi/planets['Rhea']['Period'])*r_Rhea r_Yrhe=r_Ysat+math.cos(t*2*math.pi/planets['Rhea']['Period'])*r_Rhea print("fillcircle",r_Xrhe,r_Yrhe,3) print("text ", "\"Rhea\"",r_Xrhe+planets['Rhea']['Radius']*scale,r_Yrhe) if "Titan" in planets: r_Titan=planets['Titan']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Titan) r_Xtit=r_Xsat+math.sin(t*2*math.pi/planets['Titan']['Period'])*r_Titan r_Ytit=r_Ysat+math.cos(t*2*math.pi/planets['Titan']['Period'])*r_Titan print("fillcircle",r_Xtit,r_Ytit,3) print("text ", "\"Titan\"",r_Xtit+planets['Titan']['Radius']*scale,r_Ytit) if "Iapetus" in planets: r_Iapetus=planets['Iapetus']['Orbital Radius']*scale; print("circle",r_Xsat,r_Ysat,r_Iapetus) r_Xiap=r_Xsat+math.sin(t*2*math.pi/planets['Iapetus']['Period'])*r_Iapetus r_Yiap=r_Ysat+math.cos(t*2*math.pi/planets['Iapetus']['Period'])*r_Iapetus print("fillcircle",r_Xiap,r_Yiap,3) print("text ", "\"Iapetus\"",r_Xiap+planets['Iapetus']['Radius']*scale,r_Yiap) if "Uranus" in planets: r_Uranus=planets['Uranus']['Orbital Radius']*scale; print("circle",x,y,r_Uranus) r_Xura=x+math.sin(t*2*math.pi/planets['Uranus']['Period'])*r_Uranus r_Yura=y+math.cos(t*2*math.pi/planets['Uranus']['Period'])*r_Uranus print("fillcircle",r_Xura,r_Yura,3) print("text ", "\"Uranus\"",r_Xura+planets['Uranus']['Radius']*scale,r_Yura) if "Puck" in planets: r_Puck=planets['Puck']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Puck) r_Xpuc=r_Xura+math.sin(t*2*math.pi/planets['Puck']['Period'])*r_Puck r_Ypuc=r_Yura+math.cos(t*2*math.pi/planets['Puck']['Period'])*r_Puck print("fillcircle",r_Xpuc,r_Ypuc,3) print("text ", "\"Puck\"",r_Xpuc+planets['Puck']['Radius']*scale,r_Ypuc) if "Miranda" in planets: r_Miranda=planets['Miranda']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Miranda) r_Xmira=r_Xura+math.sin(t*2*math.pi/planets['Miranda']['Period'])*r_Miranda r_Ymira=r_Yura+math.cos(t*2*math.pi/planets['Miranda']['Period'])*r_Miranda print("fillcircle",r_Xmira,r_Ymira,3) print("text ", "\"Miranda\"",r_Xmira+planets['Miranda']['Radius']*scale,r_Ymira) if "Ariel" in planets: r_Ariel=planets['Ariel']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Ariel) r_Xari=r_Xura+math.sin(t*2*math.pi/planets['Ariel']['Period'])*r_Ariel r_Yari=r_Yura+math.cos(t*2*math.pi/planets['Ariel']['Period'])*r_Ariel print("fillcircle",r_Xari,r_Yari,3) print("text ", "\"Ariel\"",r_Xari+planets['Ariel']['Radius']*scale,r_Yari) if "Umbriel" in planets: r_Umbriel=planets['Umbriel']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Umbriel) r_Xumb=r_Xura+math.sin(t*2*math.pi/planets['Umbriel']['Period'])*r_Umbriel r_Yumb=r_Yura+math.cos(t*2*math.pi/planets['Umbriel']['Period'])*r_Umbriel print("fillcircle",r_Xumb,r_Yumb,3) print("text ", "\"Umbriel\"",r_Xumb+planets['Umbriel']['Radius']*scale,r_Yumb) if "Titania" in planets: r_Titania=planets['Titania']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Titania) r_Xtita=r_Xura+math.sin(t*2*math.pi/planets['Titania']['Period'])*r_Titania r_Ytita=r_Yura+math.cos(t*2*math.pi/planets['Titania']['Period'])*r_Titania print("fillcircle",r_Xtita,r_Ytita,3) print("text ", "\"Titania\"",r_Xtita+planets['Titania']['Radius']*scale,r_Ytita) if "Oberon" in planets: r_Oberon=planets['Oberon']['Orbital Radius']*scale; print("circle",r_Xura,r_Yura,r_Oberon) r_Xober=r_Xura+math.sin(t*2*math.pi/planets['Oberon']['Period'])*r_Oberon r_Yober=r_Yura+math.cos(t*2*math.pi/planets['Oberon']['Period'])*r_Oberon print("fillcircle",r_Xober,r_Yober,3) print("text ", "\"Oberon\"",r_Xober+planets['Oberon']['Radius']*scale,r_Yober) if "Neptune" in planets: r_Neptune=planets['Neptune']['Orbital Radius']*scale; print("circle",x,y,r_Neptune) r_Xnep=x+math.sin(t*2*math.pi/planets['Neptune']['Period'])*r_Neptune r_Ynep=y+math.cos(t*2*math.pi/planets['Neptune']['Period'])*r_Neptune print("fillcircle",r_Xnep,r_Ynep,3) print("text ", "\"Neptune\"",r_Xnep+planets['Neptune']['Radius']*scale,r_Ynep) if "Titan" in planets: r_Titan=planets['Titan']['Orbital Radius']*scale; print("circle",r_Xnep,r_Ynep,r_Titan) r_Xtita=r_Xnep+math.sin(t*2*math.pi/planets['Titan']['Period'])*r_Titan r_Ytita=r_Ynep+math.cos(t*2*math.pi/planets['Titan']['Period'])*r_Titan print("fillcircle",r_Xtita,r_Ytita,3) print("text ", "\"Titan\"",r_Xtita+planets['Titan']['Radius']*scale,r_Ytita) t += 0.003 print(draw(x, y, t, planets))

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  • How to deploy jBPM 3.2.2 console on Oracle 10g iAS

    - by Balint Pato
    Hi! Does anybody have experience regarding deployment of the jBPM Administration Console on Oracle 10g iAS? I successfully deployed it using an .ear, security mappings working, I can even login to the console, Hibernate finds the JNDI datasource but it cannot find the TransactionManager. I see no log, only the exception thrown in the jsf page: Can anybody help me? The hibernate.cfg.xml file now looks like this: <?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- hibernate dialect --> <property name="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</property> <!-- JDBC connection properties (begin) === <property name="hibernate.connection.driver_class">org.hsqldb.jdbcDriver</property> <property name="hibernate.connection.url">jdbc:hsqldb:mem:jbpm</property> <property name="hibernate.connection.username">sa</property> <property name="hibernate.connection.password"></property> ==== JDBC connection properties (end) --> <property name="hibernate.cache.provider_class">org.hibernate.cache.HashtableCacheProvider</property> <!-- DataSource properties (begin) --> <property name="hibernate.connection.datasource">java:/JbpmDS</property> <!-- DataSource properties (end) --> <!-- JTA transaction properties (begin) --> <property name="hibernate.transaction.factory_class">org.hibernate.transaction.JTATransactionFactory</property> <!-- <property name="hibernate.transaction.manager_lookup_class">org.hibernate.transaction.JBossTransactionManagerLookup</property>--> <!-- JTA transaction properties (end) --> <!-- CMT transaction properties (begin) === <property name="hibernate.transaction.factory_class">org.hibernate.transaction.CMTTransactionFactory</property> <property name="hibernate.transaction.manager_lookup_class">org.hibernate.transaction.JBossTransactionManagerLookup</property> ==== CMT transaction properties (end) --> <!-- logging properties (begin) --> <property name="hibernate.show_sql">true</property> <property name="hibernate.format_sql">true</property> <property name="hibernate.use_sql_comments">true</property> <--==== logging properties (end) --> <!-- ############################################ --> <!-- # mapping files with external dependencies # --> <!-- ############################################ --> <!-- following mapping file has a dependendy on --> <!-- 'bsh-{version}.jar'. --> <!-- uncomment this if you don't have bsh on your --> <!-- classpath. you won't be able to use the --> <!-- script element in process definition files --> <mapping resource="org/jbpm/graph/action/Script.hbm.xml"/> <!-- following mapping files have a dependendy on --> <!-- 'jbpm-identity.jar', mapping files --> <!-- of the pluggable jbpm identity component. --> <!-- Uncomment the following 3 lines if you --> <!-- want to use the jBPM identity mgmgt --> <!-- component. --> <!-- identity mappings (begin) --> <mapping resource="org/jbpm/identity/User.hbm.xml"/> <mapping resource="org/jbpm/identity/Group.hbm.xml"/> <mapping resource="org/jbpm/identity/Membership.hbm.xml"/> <!-- identity mappings (end) --> <!-- following mapping files have a dependendy on --> <!-- the JCR API --> <!-- jcr mappings (begin) === <mapping resource="org/jbpm/context/exe/variableinstance/JcrNodeInstance.hbm.xml"/> ==== jcr mappings (end) --> <!-- ###################### --> <!-- # jbpm mapping files # --> <!-- ###################### --> <!-- hql queries and type defs --> <mapping resource="org/jbpm/db/hibernate.queries.hbm.xml" /> <!-- graph.action mapping files --> <mapping resource="org/jbpm/graph/action/MailAction.hbm.xml"/> <!-- graph.def mapping files --> <mapping resource="org/jbpm/graph/def/ProcessDefinition.hbm.xml"/> <mapping resource="org/jbpm/graph/def/Node.hbm.xml"/> <mapping resource="org/jbpm/graph/def/Transition.hbm.xml"/> <mapping resource="org/jbpm/graph/def/Event.hbm.xml"/> <mapping resource="org/jbpm/graph/def/Action.hbm.xml"/> <mapping resource="org/jbpm/graph/def/SuperState.hbm.xml"/> <mapping resource="org/jbpm/graph/def/ExceptionHandler.hbm.xml"/> <mapping resource="org/jbpm/instantiation/Delegation.hbm.xml"/> <!-- graph.node mapping files --> <mapping resource="org/jbpm/graph/node/StartState.hbm.xml"/> <mapping resource="org/jbpm/graph/node/EndState.hbm.xml"/> <mapping resource="org/jbpm/graph/node/ProcessState.hbm.xml"/> <mapping resource="org/jbpm/graph/node/Decision.hbm.xml"/> <mapping resource="org/jbpm/graph/node/Fork.hbm.xml"/> <mapping resource="org/jbpm/graph/node/Join.hbm.xml"/> <mapping resource="org/jbpm/graph/node/MailNode.hbm.xml"/> <mapping resource="org/jbpm/graph/node/State.hbm.xml"/> <mapping resource="org/jbpm/graph/node/TaskNode.hbm.xml"/> <!-- context.def mapping files --> <mapping resource="org/jbpm/context/def/ContextDefinition.hbm.xml"/> <mapping resource="org/jbpm/context/def/VariableAccess.hbm.xml"/> <!-- taskmgmt.def mapping files --> <mapping resource="org/jbpm/taskmgmt/def/TaskMgmtDefinition.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/def/Swimlane.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/def/Task.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/def/TaskController.hbm.xml"/> <!-- module.def mapping files --> <mapping resource="org/jbpm/module/def/ModuleDefinition.hbm.xml"/> <!-- bytes mapping files --> <mapping resource="org/jbpm/bytes/ByteArray.hbm.xml"/> <!-- file.def mapping files --> <mapping resource="org/jbpm/file/def/FileDefinition.hbm.xml"/> <!-- scheduler.def mapping files --> <mapping resource="org/jbpm/scheduler/def/CreateTimerAction.hbm.xml"/> <mapping resource="org/jbpm/scheduler/def/CancelTimerAction.hbm.xml"/> <!-- graph.exe mapping files --> <mapping resource="org/jbpm/graph/exe/Comment.hbm.xml"/> <mapping resource="org/jbpm/graph/exe/ProcessInstance.hbm.xml"/> <mapping resource="org/jbpm/graph/exe/Token.hbm.xml"/> <mapping resource="org/jbpm/graph/exe/RuntimeAction.hbm.xml"/> <!-- module.exe mapping files --> <mapping resource="org/jbpm/module/exe/ModuleInstance.hbm.xml"/> <!-- context.exe mapping files --> <mapping resource="org/jbpm/context/exe/ContextInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/TokenVariableMap.hbm.xml"/> <mapping resource="org/jbpm/context/exe/VariableInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/variableinstance/ByteArrayInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/variableinstance/DateInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/variableinstance/DoubleInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/variableinstance/HibernateLongInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/variableinstance/HibernateStringInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/variableinstance/LongInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/variableinstance/NullInstance.hbm.xml"/> <mapping resource="org/jbpm/context/exe/variableinstance/StringInstance.hbm.xml"/> <!-- job mapping files --> <mapping resource="org/jbpm/job/Job.hbm.xml"/> <mapping resource="org/jbpm/job/Timer.hbm.xml"/> <mapping resource="org/jbpm/job/ExecuteNodeJob.hbm.xml"/> <mapping resource="org/jbpm/job/ExecuteActionJob.hbm.xml"/> <!-- taskmgmt.exe mapping files --> <mapping resource="org/jbpm/taskmgmt/exe/TaskMgmtInstance.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/exe/TaskInstance.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/exe/PooledActor.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/exe/SwimlaneInstance.hbm.xml"/> <!-- logging mapping files --> <mapping resource="org/jbpm/logging/log/ProcessLog.hbm.xml"/> <mapping resource="org/jbpm/logging/log/MessageLog.hbm.xml"/> <mapping resource="org/jbpm/logging/log/CompositeLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/ActionLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/NodeLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/ProcessInstanceCreateLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/ProcessInstanceEndLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/ProcessStateLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/SignalLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/TokenCreateLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/TokenEndLog.hbm.xml"/> <mapping resource="org/jbpm/graph/log/TransitionLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/VariableLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/VariableCreateLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/VariableDeleteLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/VariableUpdateLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/variableinstance/ByteArrayUpdateLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/variableinstance/DateUpdateLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/variableinstance/DoubleUpdateLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/variableinstance/HibernateLongUpdateLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/variableinstance/HibernateStringUpdateLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/variableinstance/LongUpdateLog.hbm.xml"/> <mapping resource="org/jbpm/context/log/variableinstance/StringUpdateLog.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/log/TaskLog.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/log/TaskCreateLog.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/log/TaskAssignLog.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/log/TaskEndLog.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/log/SwimlaneLog.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/log/SwimlaneCreateLog.hbm.xml"/> <mapping resource="org/jbpm/taskmgmt/log/SwimlaneAssignLog.hbm.xml"/> </session-factory> </hibernate-configuration> ---- edit --- I have already tried the hibernate.transaction.manager_lookup_class to set to the JBoss version (org.hibernate.transaction.JBossTransactionManagerLookup) it did not work...well it's not that suprising...I'll try now: org.hibernate.transaction.OC4JTransactionManagerLookup I tried with CMT instead of JTA, but it didn't work also.

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  • Beginning Java (Working with Arrays; Class Assignment)

    - by Jason
    I am to the point where I feel as if I correctly wrote the code for this homework assignment. We were given a skeleton and 2 classes that we had to import (FileIOHelper and Student). /* * Created: *** put the date here *** * * Author: *** put your name here *** * * The program will read information about students and their * scores from a file, and output the name of each student with * all his/her scores and the total score, plus the average score * of the class, and the name and total score of the students with * the highest and lowest total score. */ // import java.util.Scanner; import java.io.*; // C:\Users\Adam\info.txt public class Lab6 { public static void main(String[] args) throws IOException { // Fill in the body according to the following comments Scanner key boardFile = new Scanner(System.in); // Input file name String filename = getFileName(keyboardFile); //Open the file // Input number of students int numStudents = FileIOHelper.getNumberOfStudents(filename); Student students[] = new Student[numStudents]; // Input all student records and create Student array and // integer array for total scores int totalScore[] = new int[students.length]; for (int i = 0; i < students.length; i++){ for(int j = 1; j < 4; j++){ totalScore[i] = totalScore[i] + students[i].getScore(j); } } // Compute total scores and find students with lowest and // highest total score int maxScore = 0; int minScore = 0; for(int i = 0; i < students.length; i++){ if(totalScore[i] >= totalScore[maxScore]){ maxScore = i; } else if(totalScore[i] <= totalScore[minScore]){ minScore = i; } } // Compute average total score int allScores = 0; int average = 0; for (int i = 0; i < totalScore.length; i++){ allScores = allScores + totalScore[i]; } average = allScores / totalScore.length; // Output results outputResults(students, totalScore, maxScore, minScore, average); } // Given a Scanner in, this method prompts the user to enter // a file name, inputs it, and returns it. private static String getFileName(Scanner in) { // Fill in the body System.out.print("Enter the name of a file: "); String filename = in.next(); return filename; // Do not declare the Scanner variable in this method. // You must use the value this method receives in the // argument (in). } // Given the number of students records n to input, this // method creates an array of Student of the appropriate size, // reads n student records using the FileIOHelper, and stores // them in the array, and finally returns the Student array. private static Student[] getStudents(int n) { Student[] myStudents = new Student[n]; for(int i = 0; i <= n; i++){ myStudents[i] = FileIOHelper.getNextStudent(); } return myStudents; } // Given an array of Student records, an array with the total scores, // the indices in the arrays of the students with the highest and // lowest total scores, and the average total score for the class, // this method outputs a table of all the students appropriately // formatted, plus the total number of students, the average score // of the class, and the name and total score of the students with // the highest and lowest total score. private static void outputResults( Student[] students, int[] totalScores, int maxIndex, int minIndex, int average ) { // Fill in the body System.out.println("\nName \t\tScore1 \tScore2 \tScore3 \tTotal"); System.out.println("--------------------------------------------------------"); for(int i = 0; i < students.length; i++){ outputStudent(students[i], totalScores[i], average); System.out.println(); } System.out.println("--------------------------------------------------------"); outputNumberOfStudents(students.length); outputAverage(average); outputMaxStudent(students[maxIndex], totalScores[maxIndex]); outputMinStudent(students[minIndex], totalScores[minIndex]); System.out.println("--------------------------------------------------------"); } // Given a Student record, the total score for the student, // and the average total score for all the students, this method // outputs one line in the result table appropriately formatted. private static void outputStudent(Student s, int total, int avg) { System.out.print(s.getName() + "\t"); for(int i = 1; i < 4; i++){ System.out.print(s.getScore(i) + "\t"); } System.out.print(total + "\t"); if(total < avg){ System.out.print("-"); }else if(total > avg){ System.out.print("+"); }else{ System.out.print("="); } } // Given the number of students, this method outputs a message // stating what the total number of students in the class is. private static void outputNumberOfStudents(int n) { System.out.println("The total number of students in this class is: \t" + n); } // Given the average total score of all students, this method // outputs a message stating what the average total score of // the class is. private static void outputAverage(int average) { System.out.println("The average total score of the class is: \t" + average); } // Given the Student with highest total score and the student's // total score, this method outputs a message stating the name // of the student and the highest score. private static void outputMaxStudent( Student student, int score ) { System.out.println(student.getName() + " got the maximum total score of: \t" + score); } // Given the Student with lowest total score and the student's // total score, this method outputs a message stating the name // of the student and the lowest score. private static void outputMinStudent( Student student, int score ) { System.out.println(student.getName() + " got the minimum total score of: \t" + score); } } But now I get an error at the line totalScore[i] = totalScore[i] + students[i].getScore(j); Exception in thread "main" java.lang.NullPointerException at Lab6.main(Lab6.java:42)

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  • Followup: Python 2.6, 3 abstract base class misunderstanding

    - by Aaron
    I asked a question at Python 2.6, 3 abstract base class misunderstanding. My problem was that python abstract base classes didn't work quite the way I expected them to. There was some discussion in the comments about why I would want to use ABCs at all, and Alex Martelli provided an excellent answer on why my use didn't work and how to accomplish what I wanted. Here I'd like to address why one might want to use ABCs, and show my test code implementation based on Alex's answer. tl;dr: Code after the 16th paragraph. In the discussion on the original post, statements were made along the lines that you don't need ABCs in Python, and that ABCs don't do anything and are therefore not real classes; they're merely interface definitions. An abstract base class is just a tool in your tool box. It's a design tool that's been around for many years, and a programming tool that is explicitly available in many programming languages. It can be implemented manually in languages that don't provide it. An ABC is always a real class, even when it doesn't do anything but define an interface, because specifying the interface is what an ABC does. If that was all an ABC could do, that would be enough reason to have it in your toolbox, but in Python and some other languages they can do more. The basic reason to use an ABC is when you have a number of classes that all do the same thing (have the same interface) but do it differently, and you want to guarantee that that complete interface is implemented in all objects. A user of your classes can rely on the interface being completely implemented in all classes. You can maintain this guarantee manually. Over time you may succeed. Or you might forget something. Before Python had ABCs you could guarantee it semi-manually, by throwing NotImplementedError in all the base class's interface methods; you must implement these methods in derived classes. This is only a partial solution, because you can still instantiate such a base class. A more complete solution is to use ABCs as provided in Python 2.6 and above. Template methods and other wrinkles and patterns are ideas whose implementation can be made easier with full-citizen ABCs. Another idea in the comments was that Python doesn't need ABCs (understood as a class that only defines an interface) because it has multiple inheritance. The implied reference there seems to be Java and its single inheritance. In Java you "get around" single inheritance by inheriting from one or more interfaces. Java uses the word "interface" in two ways. A "Java interface" is a class with method signatures but no implementations. The methods are the interface's "interface" in the more general, non-Java sense of the word. Yes, Python has multiple inheritance, so you don't need Java-like "interfaces" (ABCs) merely to provide sets of interface methods to a class. But that's not the only reason in software development to use ABCs. Most generally, you use an ABC to specify an interface (set of methods) that will likely be implemented differently in different derived classes, yet that all derived classes must have. Additionally, there may be no sensible default implementation for the base class to provide. Finally, even an ABC with almost no interface is still useful. We use something like it when we have multiple except clauses for a try. Many exceptions have exactly the same interface, with only two differences: the exception's string value, and the actual class of the exception. In many exception clauses we use nothing about the exception except its class to decide what to do; catching one type of exception we do one thing, and another except clause catching a different exception does another thing. According to the exception module's doc page, BaseException is not intended to be derived by any user defined exceptions. If ABCs had been a first class Python concept from the beginning, it's easy to imagine BaseException being specified as an ABC. But enough of that. Here's some 2.6 code that demonstrates how to use ABCs, and how to specify a list-like ABC. Examples are run in ipython, which I like much better than the python shell for day to day work; I only wish it was available for python3. Your basic 2.6 ABC: from abc import ABCMeta, abstractmethod class Super(): __metaclass__ = ABCMeta @abstractmethod def method1(self): pass Test it (in ipython, python shell would be similar): In [2]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods method1 Notice the end of the last line, where the TypeError exception tells us that method1 has not been implemented ("abstract methods method1"). That was the method designated as @abstractmethod in the preceding code. Create a subclass that inherits Super, implement method1 in the subclass and you're done. My problem, which caused me to ask the original question, was how to specify an ABC that itself defines a list interface. My naive solution was to make an ABC as above, and in the inheritance parentheses say (list). My assumption was that the class would still be abstract (can't instantiate it), and would be a list. That was wrong; inheriting from list made the class concrete, despite the abstract bits in the class definition. Alex suggested inheriting from collections.MutableSequence, which is abstract (and so doesn't make the class concrete) and list-like. I used collections.Sequence, which is also abstract but has a shorter interface and so was quicker to implement. First, Super derived from Sequence, with nothing extra: from abc import abstractmethod from collections import Sequence class Super(Sequence): pass Test it: In [6]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods __getitem__, __len__ We can't instantiate it. A list-like full-citizen ABC; yea! Again, notice in the last line that TypeError tells us why we can't instantiate it: __getitem__ and __len__ are abstract methods. They come from collections.Sequence. But, I want a bunch of subclasses that all act like immutable lists (which collections.Sequence essentially is), and that have their own implementations of my added interface methods. In particular, I don't want to implement my own list code, Python already did that for me. So first, let's implement the missing Sequence methods, in terms of Python's list type, so that all subclasses act as lists (Sequences). First let's see the signatures of the missing abstract methods: In [12]: help(Sequence.__getitem__) Help on method __getitem__ in module _abcoll: __getitem__(self, index) unbound _abcoll.Sequence method (END) In [14]: help(Sequence.__len__) Help on method __len__ in module _abcoll: __len__(self) unbound _abcoll.Sequence method (END) __getitem__ takes an index, and __len__ takes nothing. And the implementation (so far) is: from abc import abstractmethod from collections import Sequence class Super(Sequence): # Gives us a list member for ABC methods to use. def __init__(self): self._list = [] # Abstract method in Sequence, implemented in terms of list. def __getitem__(self, index): return self._list.__getitem__(index) # Abstract method in Sequence, implemented in terms of list. def __len__(self): return self._list.__len__() # Not required. Makes printing behave like a list. def __repr__(self): return self._list.__repr__() Test it: In [34]: a = Super() In [35]: a Out[35]: [] In [36]: print a [] In [37]: len(a) Out[37]: 0 In [38]: a[0] --------------------------------------------------------------------------- IndexError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() /home/aaron/projects/test/test.py in __getitem__(self, index) 10 # Abstract method in Sequence, implemented in terms of list. 11 def __getitem__(self, index): ---> 12 return self._list.__getitem__(index) 13 14 # Abstract method in Sequence, implemented in terms of list. IndexError: list index out of range Just like a list. It's not abstract (for the moment) because we implemented both of Sequence's abstract methods. Now I want to add my bit of interface, which will be abstract in Super and therefore required to implement in any subclasses. And we'll cut to the chase and add subclasses that inherit from our ABC Super. from abc import abstractmethod from collections import Sequence class Super(Sequence): # Gives us a list member for ABC methods to use. def __init__(self): self._list = [] # Abstract method in Sequence, implemented in terms of list. def __getitem__(self, index): return self._list.__getitem__(index) # Abstract method in Sequence, implemented in terms of list. def __len__(self): return self._list.__len__() # Not required. Makes printing behave like a list. def __repr__(self): return self._list.__repr__() @abstractmethod def method1(): pass class Sub0(Super): pass class Sub1(Super): def __init__(self): self._list = [1, 2, 3] def method1(self): return [x**2 for x in self._list] def method2(self): return [x/2.0 for x in self._list] class Sub2(Super): def __init__(self): self._list = [10, 20, 30, 40] def method1(self): return [x+2 for x in self._list] We've added a new abstract method to Super, method1. This makes Super abstract again. A new class Sub0 which inherits from Super but does not implement method1, so it's also an ABC. Two new classes Sub1 and Sub2, which both inherit from Super. They both implement method1 from Super, so they're not abstract. Both implementations of method1 are different. Sub1 and Sub2 also both initialize themselves differently; in real life they might initialize themselves wildly differently. So you have two subclasses which both "is a" Super (they both implement Super's required interface) although their implementations are different. Also remember that Super, although an ABC, provides four non-abstract methods. So Super provides two things to subclasses: an implementation of collections.Sequence, and an additional abstract interface (the one abstract method) that subclasses must implement. Also, class Sub1 implements an additional method, method2, which is not part of Super's interface. Sub1 "is a" Super, but it also has additional capabilities. Test it: In [52]: a = Super() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Super with abstract methods method1 In [53]: a = Sub0() --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: Can't instantiate abstract class Sub0 with abstract methods method1 In [54]: a = Sub1() In [55]: a Out[55]: [1, 2, 3] In [56]: b = Sub2() In [57]: b Out[57]: [10, 20, 30, 40] In [58]: print a, b [1, 2, 3] [10, 20, 30, 40] In [59]: a, b Out[59]: ([1, 2, 3], [10, 20, 30, 40]) In [60]: a.method1() Out[60]: [1, 4, 9] In [61]: b.method1() Out[61]: [12, 22, 32, 42] In [62]: a.method2() Out[62]: [0.5, 1.0, 1.5] [63]: a[:2] Out[63]: [1, 2] In [64]: a[0] = 5 --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /home/aaron/projects/test/<ipython console> in <module>() TypeError: 'Sub1' object does not support item assignment Super and Sub0 are abstract and can't be instantiated (lines 52 and 53). Sub1 and Sub2 are concrete and have an immutable Sequence interface (54 through 59). Sub1 and Sub2 are instantiated differently, and their method1 implementations are different (60, 61). Sub1 includes an additional method2, beyond what's required by Super (62). Any concrete Super acts like a list/Sequence (63). A collections.Sequence is immutable (64). Finally, a wart: In [65]: a._list Out[65]: [1, 2, 3] In [66]: a._list = [] In [67]: a Out[67]: [] Super._list is spelled with a single underscore. Double underscore would have protected it from this last bit, but would have broken the implementation of methods in subclasses. Not sure why; I think because double underscore is private, and private means private. So ultimately this whole scheme relies on a gentleman's agreement not to reach in and muck with Super._list directly, as in line 65 above. Would love to know if there's a safer way to do that.

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  • Flash IO error while uploading photo with low uploading internet speed

    - by Beck
    Actionscript: System.security.allowDomain("http://" + _root.tdomain + "/"); import flash.net.FileReferenceList; import flash.net.FileReference; import flash.external.ExternalInterface; import flash.external.*; /* Main variables */ var session_photos = _root.ph; var how_much_you_can_upload = 0; var selected_photos; // container for selected photos var inside_photo_num = 0; // for photo in_array selection var created_elements = _root.ph; var for_js_num = _root.ph; /* Functions & settings for javascript<->flash conversation */ var methodName:String = "addtoflash"; var instance:Object = null; var method:Function = addnewphotonumber; var wasSuccessful:Boolean = ExternalInterface.addCallback(methodName, instance, method); function addnewphotonumber() { session_photos--; created_elements--; for_js_num--; } /* Javascript hide and show flash button functions */ function block(){getURL("Javascript: blocking();");} function unblock(){getURL("Javascript:unblocking();");} /* Creating HTML platform function */ var result = false; /* Uploading */ function uploadthis(photos:Array) { if(!photos[inside_photo_num].upload("http://" + _root.tdomain + "/upload.php?PHPSESSID=" + _root.phpsessionid)) { getURL("Javascript:error_uploading();"); } } /* Flash button(applet) options and bindings */ var fileTypes:Array = new Array(); var imageTypes:Object = new Object(); imageTypes.description = "Images (*.jpg)"; imageTypes.extension = "*.jpg;"; fileTypes.push(imageTypes); var fileListener:Object = new Object(); var btnListener:Object = new Object(); btnListener.click = function(eventObj:Object) { var fileRef:FileReferenceList = new FileReferenceList(); fileRef.addListener(fileListener); fileRef.browse(fileTypes); } uploadButton.addEventListener("click", btnListener); /* Listeners */ fileListener.onSelect = function(fileRefList:FileReferenceList):Void { // reseting values inside_photo_num = 0; var list:Array = fileRefList.fileList; var item:FileReference; // PHP photo counter how_much_you_can_upload = 3 - session_photos; if(list.length > how_much_you_can_upload) { getURL("Javascript:howmuch=" + how_much_you_can_upload + ";list_length=" + list.length + ";limit_reached();"); return; } // if session variable isn't yet refreshed, we check inner counter if(created_elements >= 3) { getURL("Javascript:limit_reached();"); return; } selected_photos = list; for(var i:Number = 0; i < list.length; i++) { how_much_you_can_upload--; item = list[i]; trace("name: " + item.name); trace(item.addListener(this)); if((item.size / 1024) > 5000) {getURL("Javascript:size_limit_reached();");return;} } result = false; setTimeout(block,500); /* Increment number for new HTML container and pass it to javascript, after javascript returns true and we start uploading */ for_js_num++; if(ExternalInterface.call("create_platform",for_js_num)) { uploadthis(selected_photos); } } fileListener.onProgress = function(file:FileReference, bytesLoaded:Number, bytesTotal:Number):Void { getURL("Javascript:files_process(" + bytesLoaded + "," + bytesTotal + "," + for_js_num + ");"); } fileListener.onComplete = function(file:FileReference, bytesLoaded:Number, bytesTotal:Number):Void { inside_photo_num++; var sendvar_lv:LoadVars = new LoadVars(); var loadvar_lv:LoadVars = new LoadVars(); loadvar_lv.onLoad = function(success:Boolean){ if(loadvar_lv.failed == 1) { getURL("Javascript:type_failed();"); return; } getURL("Javascript:filelinks='" + loadvar_lv.json + "';fullname='" + loadvar_lv.fullname + "';completed(" + for_js_num + ");"); created_elements++; if((inside_photo_num + 1) > selected_photos.length) {setTimeout(unblock,1000);return;} // don't create empty containers anymore if(created_elements >= 3) {return;} result = false; /* Increment number for new HTML container and pass it to javascript, after javascript returns true and we start uploading */ for_js_num++; if(ExternalInterface.call("create_platform",for_js_num)) { uploadthis(selected_photos); } } sendvar_lv.getnum = true; sendvar_lv.PHPSESSID = _root.phpsessionid; sendvar_lv.sendAndLoad("http://" + _root.tdomain + "/upload.php",loadvar_lv,"POST"); } fileListener.onCancel = function(file:FileReference):Void { } fileListener.onOpen = function(file:FileReference):Void { } fileListener.onHTTPError = function(file:FileReference, httpError:Number):Void { getURL("Javascript:http_error(" + httpError + ");"); } fileListener.onSecurityError = function(file:FileReference, errorString:String):Void { getURL("Javascript:security_error(" + errorString + ");"); } fileListener.onIOError = function(file:FileReference):Void { getURL("Javascript:io_error();"); selected_photos[inside_photo_num].cancel(); uploadthis(selected_photos); } <PARAM name="allowScriptAccess" value="always"> <PARAM name="swliveconnect" value="true"> <PARAM name="movie" value="http://www.localh.com/fileref.swf?ph=0&phpsessionid=8mirsjsd75v6vk583vkus50qbb2djsp6&tdomain=www.localh.com"> <PARAM name="wmode" value="opaque"> <PARAM name="quality" value="high"> <PARAM name="bgcolor" value="#ffffff"> <EMBED swliveconnect="true" wmode="opaque" src="http://www.localh.com/fileref.swf?ph=0&phpsessionid=8mirsjsd75v6vk583vkus50qbb2djsp6&tdomain=www.localh.com" quality="high" bgcolor="#ffffff" width="100" height="22" name="fileref" align="middle" allowScriptAccess="always" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer"></EMBED> My uploading speed is 40kb/sec Getting flash error while uploading photos bigger than 500kb and getting no error while uploading photos less than 100-500kb~. My friend has 8mbit uploading speed and has no errors even while uploading 3.2mb photos and more. How to fix this problem? I have tried to re-upload on IO error trigger, but it stops at the same place. Any solution regarding this error? By the way, i was watching process via debugging proxy and figured out, that responce headers doesn't come at all on this IO error. And sometimes shows socket error. If need, i will post serverside php script as well. But it stops at if(isset($_FILES['Filedata'])) { so it won't help :) as all processing comes after this check.

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  • Postgres cannot connect to server

    - by user1408935
    Super stumped by why Postgres isn't working on a new app I just started. I've got it working for one app already. I'm using postgres.app, and it's running. I started a new app with rails new depot -d postgresql and then I went into the database.yml file and changed username to my $USER (which is what it is for the other app, which is working). So now my database.yml file has this development section: development: adapter: postgresql encoding: unicode database: depot_development pool: 5 username: <username> password: But when I run "rake db:create" or "rake db:create:all" I still got this error (in full, cause I don't know what's relevant): Couldn't create database for {"adapter"=>"postgresql", "encoding"=>"unicode", "database"=>"depot_development", "pool"=>5, "username"=>"<username>", "password"=>nil} could not connect to server: Permission denied Is the server running locally and accepting connections on Unix domain socket "/var/pgsql_socket/.s.PGSQL.5432"? /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:1213:in `initialize' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:1213:in `new' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:1213:in `connect' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:329:in `initialize' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `new' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/postgresql_adapter.rb:28:in `postgresql_connection' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:309:in `new_connection' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:319:in `checkout_new_connection' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:241:in `block (2 levels) in checkout' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:236:in `loop' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:236:in `block in checkout' /Users/<username>/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:233:in `checkout' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:96:in `block in connection' /Users/<username>/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:95:in `connection' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_pool.rb:404:in `retrieve_connection' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_specification.rb:170:in `retrieve_connection' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/connection_adapters/abstract/connection_specification.rb:144:in `connection' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/railties/databases.rake:107:in `rescue in create_database' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/railties/databases.rake:51:in `create_database' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/railties/databases.rake:40:in `block (3 levels) in <top (required)>' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/railties/databases.rake:40:in `each' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.8/lib/active_record/railties/databases.rake:40:in `block (2 levels) in <top (required)>' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:205:in `call' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:205:in `block in execute' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:200:in `each' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:200:in `execute' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:158:in `block in invoke_with_call_chain' /Users/<username>/.rvm/rubies/ruby-1.9.3-p194/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:151:in `invoke_with_call_chain' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/task.rb:144:in `invoke' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:116:in `invoke_task' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `block (2 levels) in top_level' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `each' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `block in top_level' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:88:in `top_level' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:66:in `block in run' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/lib/rake/application.rb:63:in `run' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/gems/rake-0.9.2.2/bin/rake:33:in `<top (required)>' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/bin/rake:19:in `load' /Users/<username>/.rvm/gems/ruby-1.9.3-p194@global/bin/rake:19:in `<main>' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/bin/ruby_noexec_wrapper:14:in `eval' /Users/<username>/.rvm/gems/ruby-1.9.3-p194/bin/ruby_noexec_wrapper:14:in `<main>' Couldn't create database for {"adapter"=>"postgresql", "encoding"=>"unicode", "database"=>"depot_test", "pool"=>5, "username"=>"<username>", "password"=>nil} I have tried createdb depot_development I have tried going into the psql environment and listing users (which included my username among them). In the same psql environment, I tried CREATE DATABASE depot; I've made sure that the pg gem is installed with bundle install, I've run "pg_ctl start", to which I got this response: pg_ctl: no database directory specified and environment variable PGDATA unset I ran "ps aux | grep postgres" to make sure postgres was running, to which I got this in return (which looks like it's doing OK, right?): <username> 10390 0.4 0.0 2425480 180 s000 R+ 6:15PM 0:00.00 grep postgres <username> 2907 0.0 0.0 2441604 464 ?? Ss 6:17PM 0:02.31 postgres: stats collector process <username> 2906 0.0 0.0 2445520 1664 ?? Ss 6:17PM 0:02.33 postgres: autovacuum launcher process <username> 2905 0.0 0.0 2445388 600 ?? Ss 6:17PM 0:09.25 postgres: wal writer process <username> 2904 0.0 0.0 2445388 1252 ?? Ss 6:17PM 0:12.08 postgres: writer process <username> 2902 0.0 0.0 2445388 3688 ?? S 6:17PM 0:00.54 /Applications/Postgres.app/Contents/MacOS/bin/postgres -D /Users/<username>/Library/Application Support/Postgres/var -p5432 The short of it, is I've been troubleshooting for a WHILE and have NO idea what's wrong. Any ideas? I'd really appreciate it, cause I'm pretty new to Rails, and this is a pretty disheartening roadblock. Thanks! EDIT -- Per request, posting the successful database.yml . It seems the difference is the inclusion of a password: development: adapter: postgresql encoding: unicode database: *******_development pool: 5 username: ******* password: ******* EDIT2 -- When I add a password to the .yml file, then run rake db:create again, I get this error. rake aborted! No Rakefile found (looking for: rakefile, Rakefile, rakefile.rb, Rakefile.rb)

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  • Why won't "!important" override ":first-line"?

    - by bazzlevi
    I am trying to do the tutorial in Chapter 6 of the 2nd edition of "CSS: The Missing Manual", and I've run into an issue I'm trying to understand. I have one style that looks like this: #main p:first-line { color: #999999; font-weight: bold; } Later I have another style that looks like this: #main p.byline { color: #00994D !important; font-size: 1.6em; margin: 5px 0 25px 50px; } I am confused because the second one won't override the color choice in the first one despite the fact that the second one has "!important" in it. I put both classes into an online specificity calculator, and the second one comes out being more specific, so I'm doubly confused. By the way, the inclusion of "!important" is the work-around suggested in the errata for the book. Odd that it still doesn't work! Here's the code for the entire page: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>CSS Typography</title> <style type="text/css"> html, body, h1, h2, h3, h4, h5, h6, p, ol, ul, li, pre, code, address, variable, form, fieldset, blockquote { padding: 0; margin: 0; font-size: 100%; font-weight: normal; } table { border-collapse: collapse; border-spacing: 0; } td, th, caption { font-weight: normal; text-align: left; } img, fieldset { border: 0; } ol { padding-left: 1.4em; list-style: decimal; } ul { padding-left: 1.4em; list-style:square; } q:before, q:after { content:''; } body { color: #002D4B; font-family: Arial, Helvetica, sans-serif; font-size: 62.5% } #main h1 { color: #F60; font-family: "Arial Black", Arial, Helvetica, sans-serif; font-size: 4em; } #main h2 { font: bold 3.5em "Hoefler Text", Garamond, Times, serif; border-bottom: 1px solid #002D4B; margin-top: 25px; } #main h3 { color: #F60; font-size: 1.9em; font-weight: bold; text-transform: uppercase; margin-top: 25px; margin-bottom: 10px; } #main p { font-size: 1.5em; line-height: 150%; margin-left: 150px; margin-right: 50px; margin-bottom: 10px; } #main p:first-line { color: #999999; font-weight: bold; } #main ul { margin: 50px 0 25px 50px; width: 150px; float: right; } #main li { color: #207EBF; font-size: 1.5em; margin-bottom: 7px; } #main p.byline { color: #00994D !important; font-size: 1.6em; margin: 5px 0 25px 50px; } #main .byline strong { color: #207EBF; text-transform: uppercase; margin-left: 5px; } </style> </head> <body> <div id="main"> <h1><strong>CSS</strong> The Missing Manual</h1> <h2>Exploring Typographic Possibilities</h2> <p class="byline">november 30 <strong>Rod Dibble</strong></p> <ul> <li>Lorem Ipsum</li> <li>Reprehenderit qui in ea</li> <li>Lorem Ipsum</li> <li>Reprehenderit qui in ea</li> <li>Lorem Ipsum</li> <li>Reprehenderit qui in ea</li> </ul> <h3>Esse quam nulla</h3> <p>Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas nulla pariatur? Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas nulla pariatur?</p> <h3>Quis autem vel eum</h3> <p>Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas nulla pariatur? Ut enim ad minima veniam, quis nostrum exercitationem ullam corporis suscipit laboriosam, nisi ut aliquid ex ea commodi consequatur? Quis autem vel eum iure reprehenderit qui in ea voluptate velit esse quam nihil molestiae consequatur, vel illum qui dolorem eum fugiat quo voluptas nulla pariatur?</p> </div> </body> </html> Here is the above code on JSBin: http://jsbin.com/unexe3

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  • Simplemodal: four times on a page leads to extra "next" or "previous" button

    - by DDF
    We are experiencing a problem with each instance of the call to the simplemodal div class .basic-modal-content adding an extra next or previous button in the modal windows. We are using simplemodal in four places on a page using a common JS in the container (provided below) and a common CSS format for the modal windows. In one area we are using six "statements" in a window with a next and previous button. I would include a picture of the modal window but it's being disallowed by the system as I'm a first time poster to this forum. In the other three areas we are using three "biographies" in a similar window with the ability to see each of the three bios from each of modal windows. We are using a common Simplemodal JS script in the page which has the following code: <script> $(function() { $('a').each(function() { $(this).click(function() { $('#modal_' + this.id).modal({ overlayClose:true }); }); }); var num_divs = $('div.basic-modal-content').length; $('div.basic-modal-content').each(function(i) { /* if there is a previous div add a link to it */ if (i > 0) { /* get the ID for previous div */ var prev_id = $(this).prev('.basic-modal-content').attr('id'); /* add the link with click event */ $('<a href="#" class="simplemodal-container-prev"></a>') .click(function() { $.modal.close(); $('#' + prev_id).modal({overlayClose:true}); }) .appendTo($(this)); } /* if there is a next div add a link to it */ if (i < num_divs - 1) { /* get the ID for next div */ var next_id = $(this).next('.basic-modal-content').attr('id'); /* add the link with click event */ $('<a href="#" class="simplemodal-container-next"></a>') .click(function() { $.modal.close(); $('#' + next_id).modal({overlayClose:true}); }) .appendTo($(this)); } }); }); </script> and some CSS to create an image for each window that shows the progress bar through the ul/li list. The code to produce the above looks like this: <h1>Our HEADLINE</h1> <div id='basic-modal'> <ul> <li><a href='#' id='one'>TEXT 1</a></li> <li><a href='#' id='two'>TEXT 2</a></li> <li><a href='#' id='three'>TEXT 3</a></li> <li><a href='#' id='four'>TEXT 4</a></li> <li><a href='#' id='five'>TEXT 5</a></li> <li><a href='#' id='six'>TEXT 6</a></li> </ul> </div> <div class="basic-modal-content" id="modal_one"> <img src="link to modal_one.png" alt="progress bar"/> <h3>headline text</h3> <p>body text</p> </div> <div class="basic-modal-content" id="modal_two"> <img src="link to modal_two.png" alt="progress bar"/> <h3>headline text</h3> <p>body text</p> </div> <div> ... other divs 3 4 and 5 </div> <div class="basic-modal-content" id="modal_six"> <img src="link to modal_six.png" alt="progress bar"/> <h3>headline text</h3> <p>body text</p> </div> </div> The ul/li structure works on the main page for the links. The modal windows allow one to browse through all of the six TEXTs. There is a common CSS style to the windows and a custom image in each of the modal windows derived from the "#modal_[number] img" CSS in the form of a progress bar. It should be noted that the first modal window in the first set of ul/li (the six) do not exhibit the extra previous button. Here is the relevant code from one of the three biographic links. You will note that the biographic links each have to have all three in this current configuration. <h4>Our HEADLINE</h4> <div class="bottom-widget-text"> <img src="picture" alt="not relevant to the simplemodal problem"/> <p>Read about person NUMBER 1 by clicking on the following link: <a href='#' id='seven' >Expand</a> </p> </div> <div class="basic-modal-content" id="modal_seven"> <img src="link to modal_seven.png" alt="portrait 1"/> <h3>headline text</h3> <p>BIOGRAPHY</p> </div> <div class="basic-modal-content" id="modal_eight"> <img src="link to modal_eight.png" alt="portrait 2"/> <h3>headline text</h3> <p>BIOGRAPHY</p> </div> <div class="basic-modal-content" id="modal_nine"> <img src="link to modal_nine.png" alt="portrait 3"/> <h3>headline text</h3> <p>BIOGRAPHY</p> </div> </div> Similarly the "biographies" open up from a different area of the page. The modal windows allow one to browse through all three of the BIOs. The bios use the SAME CSS style windows and a custom image in each of the modal windows derived from the "#modal_[number] img" CSS in the form of a portrait. Everything is working well except one thing: the first six windows have an extra next button that leads to an image of the close widow button only. Similarly, the BIOs pages have extra previous button that leads to the same "close button only" shown above. We want to maintain the same base CSS for the modal windows for this page. We want to keep the JS simple. The only behavior that is bad is the extra previous and next bottons that appear to be spurious. So is this a fix to the JS? Or do I have the instances of the modal windows too entangled? Perhaps there is a better method for having multiple instances of a simplemodal window on the same page? Or is the problem the "#" variable being common to each of the uses of the JS? Thanks in advance. DDF

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  • Class member functions instantiated by traits [policies, actually]

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched Stack Overflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate member functions? [Update: I used the wrong term here. It should be "policies" rather than "traits." Traits describe existing classes. Policies prescribe synthetic classes.] The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state information was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (VC++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice? UPDATE: Here's another try at explaining it. I want the user to be able to fill out an order (manifest) for a custom optimizer, something like ordering off of a Chinese menu - one from column A, one from column B, etc.. Waiter, from column A (updaters), I'll have the BFGS update with Cholesky-decompositon sauce. From column B (line-searchers), I'll have the cubic interpolation line-search with an eta of 0.4 and a rho of 1e-4, please. Etc... UPDATE: Okay, okay. Here's the playing-around that I've done. I offer it reluctantly, because I suspect it's a completely wrong-headed approach. It runs okay under vc++ 2008. #include <boost/utility.hpp> #include <boost/type_traits/integral_constant.hpp> namespace dj { struct CBFGS { void bar() {printf("CBFGS::bar %d\n", data);} CBFGS(): data(1234){} int data; }; template<class T> struct is_CBFGS: boost::false_type{}; template<> struct is_CBFGS<CBFGS>: boost::true_type{}; struct LMQN {LMQN(): data(54.321){} void bar() {printf("LMQN::bar %lf\n", data);} double data; }; template<class T> struct is_LMQN: boost::false_type{}; template<> struct is_LMQN<LMQN> : boost::true_type{}; // "Order form" struct default_optimizer_traits { typedef CBFGS update_type; // Selection from column A - updaters }; template<class traits> class Optimizer; template<class traits> void foo(typename boost::enable_if<is_LMQN<typename traits::update_type>, Optimizer<traits> >::type& self) { printf(" LMQN %lf\n", self.data); } template<class traits> void foo(typename boost::enable_if<is_CBFGS<typename traits::update_type>, Optimizer<traits> >::type& self) { printf("CBFGS %d\n", self.data); } template<class traits = default_optimizer_traits> class Optimizer{ friend typename traits::update_type; //friend void dj::foo<traits>(typename Optimizer<traits> & self); // How? public: //void foo(void); // How??? void foo() { dj::foo<traits>(*this); } void bar() { data.bar(); } //protected: // How? typedef typename traits::update_type update_type; update_type data; }; } // namespace dj int main() { dj::Optimizer<> opt; opt.foo(); opt.bar(); std::getchar(); return 0; }

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  • Help with chat server

    - by mithun1538
    I am designing a chat server in java. The communication is Http based and not socket based. In the client side I have an applet. In the server side I have a servlet. Applet: I create a new thread to listen for incoming messages(GET method). The main thread is used to send messages(POST messages). The partial code is : public void start() { System.out.println("Creating new thread"); Thread thread = new Thread(this); thread.start(); } private String getNewMessage() { System.out.println("Inside getNewMessage"); String msg = null; try { while(msg == null) { System.out.println("Trying to listen to servlet"); URL servlet = new URL(getCodeBase(), "NewServlet?mode=msg"); URLConnection con = servlet.openConnection(); con.setUseCaches(false); DataInputStream din = new DataInputStream(new BufferedInputStream(con.getInputStream())); msg = din.readUTF(); System.out.println("message read :" + msg); } } catch (Exception e) { e.printStackTrace(); } return msg + "\n"; } public void run() { System.out.println("Inside new thread"); while(true) { System.out.println("inside first while"); String newMsg = getNewMessage(); chatOutput.append(newMsg); System.out.println("Appended!!"); } } private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { String message = chatInput.getText(); chatInput.setText(""); chatOutput.append(message + "\n"); try { System.out.println("Trying to send msg :" + message); URL url = new URL(getCodeBase(), "NewServlet"); URLConnection servletConnection = url.openConnection(); servletConnection.setDoInput(true); servletConnection.setDoOutput(true); servletConnection.setUseCaches(false); servletConnection.setRequestProperty("Content-Type", "application/octet-stream"); ObjectOutputStream out = new ObjectOutputStream(servletConnection.getOutputStream()); out.writeObject(message); out.flush(); out.close(); System.out.println("Message sent!"); } catch (Exception e) { e.printStackTrace(); } } This next code is from the servlet side. it uses the Observable interface to identify and send messages to clients. public class NewServlet extends HttpServlet { // getNextMessage() returns the next new message. // It blocks until there is one. public String getNextMessage() { // Create a message sink to wait for a new message from the // message source. System.out.println("inside getNextMessage"); return new MessageSink().getNextMessage(source);} @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("Inside Doget"); response.setContentType("text/plain"); PrintWriter out = response.getWriter(); out.println(getNextMessage()); } // broadcastMessage() informs all currently listening clients that there // is a new message. Causes all calls to getNextMessage() to unblock. public void broadcastMessage(String message) { // Send the message to all the HTTP-connected clients by giving the // message to the message source source.sendMessage(message); } @Override protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("Inside DoPost"); try { ObjectInputStream din= new ObjectInputStream(request.getInputStream()); String message = (String)din.readObject(); System.out.println("received msg"); if (message != null) broadcastMessage(message); System.out.println("Called broadcast"); // Set the status code to indicate there will be no response response.setStatus(response.SC_NO_CONTENT); } catch (Exception e) { e.printStackTrace(); } } /** * Returns a short description of the servlet. * @return a String containing servlet description */ @Override public String getServletInfo() { return "Short description"; } MessageSource source = new MessageSource();} class MessageSource extends Observable { public void sendMessage(String message) { System.out.println("inside sendMsg"); setChanged(); notifyObservers(message); } } class MessageSink implements Observer { String message = null; // set by update() and read by getNextMessage() // Called by the message source when it gets a new message synchronized public void update(Observable o, Object arg) { // Get the new message message = (String)arg; // Wake up our waiting thread notify(); } // Gets the next message sent out from the message source synchronized public String getNextMessage(MessageSource source) { // Tell source we want to be told about new messages source.addObserver(this); System.out.println("AddedObserver"); // Wait until our update() method receives a message while (message == null) { try { wait(); } catch (Exception ignored) { } } // Tell source to stop telling us about new messages source.deleteObserver(this); // Now return the message we received // But first set the message instance variable to null // so update() and getNextMessage() can be called again. String messageCopy = message; message = null; System.out.println("Returning msg"); return messageCopy; } } As you can see I have included System.out.println("Some message"); in some places. this was just for debugging purposes. In java console, i get the following output: Creating new thread Inside new thread. inside first while. Inside getNewMessage. Trying to listen to servlet. In the servlet side, i get the following output in the tomcat logs: Inside Doget. inside getNextMessage. AddedObserver. After i type a message in the applet, and send it, I get the foll output in java console: Trying to send msg :you deR?? Message sent! But in servlet side, I dont get anything in the logs. I used the O'Reily Java Servlet Programming as reference(The observer interface comes from there). But I am not getting any chat communication between two clients. As can be understood from the logs, the POST method is not called. Any reason for this?

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  • What pseudo-operators exist in Perl 5?

    - by Chas. Owens
    I am currently documenting all of Perl 5's operators (see the perlopref GitHub project) and I have decided to include Perl 5's pseudo-operators as well. To me, a pseudo-operator in Perl is anything that looks like an operator, but is really more than one operator or a some other piece of syntax. I have documented the four I am familiar with already: ()= the countof operator =()= the goatse/countof operator ~~ the scalar context operator }{ the Eskimo-kiss operator What other names exist for these pseudo-operators, and do you know of any pseudo-operators I have missed? =head1 Pseudo-operators There are idioms in Perl 5 that appear to be operators, but are really a combination of several operators or pieces of syntax. These pseudo-operators have the precedence of the constituent parts. =head2 ()= X =head3 Description This pseudo-operator is the list assignment operator (aka the countof operator). It is made up of two items C<()>, and C<=>. In scalar context it returns the number of items in the list X. In list context it returns an empty list. It is useful when you have something that returns a list and you want to know the number of items in that list and don't care about the list's contents. It is needed because the comma operator returns the last item in the sequence rather than the number of items in the sequence when it is placed in scalar context. It works because the assignment operator returns the number of items available to be assigned when its left hand side has list context. In the following example there are five values in the list being assigned to the list C<($x, $y, $z)>, so C<$count> is assigned C<5>. my $count = my ($x, $y, $z) = qw/a b c d e/; The empty list (the C<()> part of the pseudo-operator) triggers this behavior. =head3 Example sub f { return qw/a b c d e/ } my $count = ()= f(); #$count is now 5 my $string = "cat cat dog cat"; my $cats = ()= $string =~ /cat/g; #$cats is now 3 print scalar( ()= f() ), "\n"; #prints "5\n" =head3 See also L</X = Y> and L</X =()= Y> =head2 X =()= Y This pseudo-operator is often called the goatse operator for reasons better left unexamined; it is also called the list assignment or countof operator. It is made up of three items C<=>, C<()>, and C<=>. When X is a scalar variable, the number of items in the list Y is returned. If X is an array or a hash it it returns an empty list. It is useful when you have something that returns a list and you want to know the number of items in that list and don't care about the list's contents. It is needed because the comma operator returns the last item in the sequence rather than the number of items in the sequence when it is placed in scalar context. It works because the assignment operator returns the number of items available to be assigned when its left hand side has list context. In the following example there are five values in the list being assigned to the list C<($x, $y, $z)>, so C<$count> is assigned C<5>. my $count = my ($x, $y, $z) = qw/a b c d e/; The empty list (the C<()> part of the pseudo-operator) triggers this behavior. =head3 Example sub f { return qw/a b c d e/ } my $count =()= f(); #$count is now 5 my $string = "cat cat dog cat"; my $cats =()= $string =~ /cat/g; #$cats is now 3 =head3 See also L</=> and L</()=> =head2 ~~X =head3 Description This pseudo-operator is named the scalar context operator. It is made up of two bitwise negation operators. It provides scalar context to the expression X. It works because the first bitwise negation operator provides scalar context to X and performs a bitwise negation of the result; since the result of two bitwise negations is the original item, the value of the original expression is preserved. With the addition of the Smart match operator, this pseudo-operator is even more confusing. The C<scalar> function is much easier to understand and you are encouraged to use it instead. =head3 Example my @a = qw/a b c d/; print ~~@a, "\n"; #prints 4 =head3 See also L</~X>, L</X ~~ Y>, and L<perlfunc/scalar> =head2 X }{ Y =head3 Description This pseudo-operator is called the Eskimo-kiss operator because it looks like two faces touching noses. It is made up of an closing brace and an opening brace. It is used when using C<perl> as a command-line program with the C<-n> or C<-p> options. It has the effect of running X inside of the loop created by C<-n> or C<-p> and running Y at the end of the program. It works because the closing brace closes the loop created by C<-n> or C<-p> and the opening brace creates a new bare block that is closed by the loop's original ending. You can see this behavior by using the L<B::Deparse> module. Here is the command C<perl -ne 'print $_;'> deparsed: LINE: while (defined($_ = <ARGV>)) { print $_; } Notice how the original code was wrapped with the C<while> loop. Here is the deparsing of C<perl -ne '$count++ if /foo/; }{ print "$count\n"'>: LINE: while (defined($_ = <ARGV>)) { ++$count if /foo/; } { print "$count\n"; } Notice how the C<while> loop is closed by the closing brace we added and the opening brace starts a new bare block that is closed by the closing brace that was originally intended to close the C<while> loop. =head3 Example # count unique lines in the file FOO perl -nle '$seen{$_}++ }{ print "$_ => $seen{$_}" for keys %seen' FOO # sum all of the lines until the user types control-d perl -nle '$sum += $_ }{ print $sum' =head3 See also L<perlrun> and L<perlsyn> =cut

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  • TreeView in Winforms and focus problem

    - by Marcus
    Hi, Can anyone please explain to my why the form in the code below gets out of focus when selecting a treenode in the tree? What should happen is that the form/button should get the focus when the tree disappears like the listview example but it doesn't. Code example: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; namespace FocusTest { public partial class Form1 : Form { #region Generated /// <summary> /// Required designer variable. /// </summary> private System.ComponentModel.IContainer components = null; /// <summary> /// Clean up any resources being used. /// </summary> /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param> protected override void Dispose(bool disposing) { if (disposing && (components != null)) { components.Dispose(); } base.Dispose(disposing); } #region Windows Form Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { System.Windows.Forms.ListViewItem listViewItem1 = new System.Windows.Forms.ListViewItem("Item1"); System.Windows.Forms.ListViewItem listViewItem2 = new System.Windows.Forms.ListViewItem("Item2"); System.Windows.Forms.ListViewItem listViewItem3 = new System.Windows.Forms.ListViewItem("Item3"); System.Windows.Forms.TreeNode treeNode1 = new System.Windows.Forms.TreeNode("Node0"); System.Windows.Forms.TreeNode treeNode2 = new System.Windows.Forms.TreeNode("Node1"); System.Windows.Forms.TreeNode treeNode3 = new System.Windows.Forms.TreeNode("Node2"); this.button1 = new System.Windows.Forms.Button(); this.listView1 = new System.Windows.Forms.ListView(); this.button2 = new System.Windows.Forms.Button(); this.treeView1 = new System.Windows.Forms.TreeView(); this.SuspendLayout(); // // button1 // this.button1.Location = new System.Drawing.Point(12, 12); this.button1.Name = "button1"; this.button1.Size = new System.Drawing.Size(75, 23); this.button1.TabIndex = 0; this.button1.Text = "button1"; this.button1.UseVisualStyleBackColor = true; this.button1.Click += new System.EventHandler(this.button1_Click); // // listView1 // this.listView1.Items.AddRange(new System.Windows.Forms.ListViewItem[] { listViewItem1, listViewItem2, listViewItem3 }); this.listView1.Location = new System.Drawing.Point(12, 41); this.listView1.Name = "listView1"; this.listView1.Size = new System.Drawing.Size(121, 97); this.listView1.TabIndex = 1; this.listView1.UseCompatibleStateImageBehavior = false; this.listView1.Visible = false; this.listView1.SelectedIndexChanged += new System.EventHandler(this.listView1_SelectedIndexChanged); this.listView1.View = View.List; // // button2 // this.button2.Location = new System.Drawing.Point(310, 11); this.button2.Name = "button2"; this.button2.Size = new System.Drawing.Size(75, 23); this.button2.TabIndex = 2; this.button2.Text = "button2"; this.button2.UseVisualStyleBackColor = true; this.button2.Click += new System.EventHandler(this.button2_Click); // // treeView1 // this.treeView1.Location = new System.Drawing.Point(310, 41); this.treeView1.Name = "treeView1"; treeNode1.Name = "Node0"; treeNode1.Text = "Node0"; treeNode2.Name = "Node1"; treeNode2.Text = "Node1"; treeNode3.Name = "Node2"; treeNode3.Text = "Node2"; this.treeView1.Nodes.AddRange(new System.Windows.Forms.TreeNode[] { treeNode1, treeNode2, treeNode3}); this.treeView1.Size = new System.Drawing.Size(121, 97); this.treeView1.TabIndex = 3; this.treeView1.Visible = false; this.treeView1.AfterSelect += new System.Windows.Forms.TreeViewEventHandler(this.treeView1_AfterSelect); // // Form1 // this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F); this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font; this.ClientSize = new System.Drawing.Size(760, 409); this.Controls.Add(this.treeView1); this.Controls.Add(this.button2); this.Controls.Add(this.listView1); this.Controls.Add(this.button1); this.Name = "Form1"; this.Text = "Form1"; this.ResumeLayout(false); } #endregion private System.Windows.Forms.Button button1; private System.Windows.Forms.ListView listView1; private System.Windows.Forms.Button button2; private System.Windows.Forms.TreeView treeView1; #endregion public Form1() { InitializeComponent(); } #region TreeView private void button2_Click(object sender, EventArgs e) { ToggleTreeView(); } private void ToggleTreeView() { if (treeView1.Visible) { Controls.Remove(treeView1); treeView1.Visible = false; } else { Controls.Add(treeView1); treeView1.Size = new Size(300, 400); treeView1.Location = PointToClient(PointToScreen(new System.Drawing.Point(button2.Location.X, button2.Location.Y + button2.Height))); this.treeView1.BringToFront(); treeView1.Visible = true; treeView1.Select(); } } private void treeView1_AfterSelect(object sender, TreeViewEventArgs e) { ToggleTreeView(); } #endregion #region ListView private void button1_Click(object sender, EventArgs e) { ToggleListView(); } private void ToggleListView() { if (listView1.Visible) { Controls.Remove(listView1); listView1.Visible = false; } else { Controls.Add(listView1); listView1.Size = new Size(300, 400); listView1.Location = PointToClient(PointToScreen(new System.Drawing.Point(button1.Location.X, button1.Location.Y + button1.Height))); this.listView1.BringToFront(); listView1.Visible = true; listView1.Select(); } } private void listView1_SelectedIndexChanged(object sender, EventArgs e) { if (listView1.Visible) ToggleListView(); } #endregion } }

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  • PHP session not working with JQuery Ajax?

    - by Bolt_Head
    Update, Solved: After all this I found out that I was calling an old version of my code in the update ajax. 'boardControl.php' instead of 'boardUpdate.php' These are the kinds of mistakes that make programing fun. I'm writing a browser gomoku game. I have the ajax statement that allows the player to play a piece. $(document).ready(function() { $("td").live('click',function(){ var value = $(this).attr('id'); $.get('includes/boardControl.php',{play: value, bid: bid}); }); }); value = board square location bid = board ID Before creating a user login for player identification, the server side php had a temporary solution. It would rotate the piece state for the squares when clicked instead of knowing what player to create them for. After creating login stuff I set a session variable for the player's ID. I was hoping to read the session ID from the php during the ajax request and figure out what player they are from there. session_start(); ... $playerId = $_SESSION['char']; $Query=("SELECT p1, p2 FROM board WHERE bid=$bid"); $Result=mysql_query($Query); $p1 = mysql_result($Result,0,"p1"); $p2 = mysql_result($Result,0,"p2"); $newPiece = 0; //*default no player if($playerId == $p1) $newPiece = 1; if($playerId == $p2) $newPiece = 2; For some reason when I run the full web app, the pieces still cycle though, even after I deleted the code to make them cycle. Furthermore, after logging in If i manually load the php page in the browser, it modifies the database correctly (where it only plays pieces belonging to that player) and outputs the correct results. It seems to me that the session is not being carried over when used with Ajax. Yet Google searches tell me that, sessions do work with Ajax. Update: I'm trying to provide more information. Logging in works correctly. My ID is recognized and I printed it out next to the board to ensure that I was retrieving it correctly. The ajax request does update the board. The values passed are correct and confirmed with firebug's console. However instead of placing pieces only for the player they belong to it cycles though the piece states (0,1,2). When manually browsing to boardUpdate.php and putting in the same values sent from the Ajax the results seen in the echo'ed response indicates that the corresponding piece is played each time as intended. Same results on my laptop after fresh load of firefox. Manually browsing to boardUpdate.php without logging in before hand leave the board unchanged (as intended when no user is found in the session). I've double checked the that session_start() is on the php files and double checked the session ID variables. Hope this extra information helps, i'm running out of ideas what to tell you. Should I load up the full code? Update 2: After checking the Ajax responce in fire-bug I realized that the 'play' request does not get a result, and the board is not updated till the next 'update'. I'm still looking into this but I'll post it here for you guys too. boardUpdate.php Notable places are: Refresh Board(line6) Place Piece(line20) function boardUpdate($turnCount) (line63) <?php session_start(); require '../../omok/dbConnect.php'; //*** Refresh Board *** if(isset($_GET['update'])) { $bid = $_GET['bid']; $Query=("SELECT turn FROM board WHERE bid=$bid"); $Result=mysql_query($Query); $turnCount=mysql_result($Result,0,"turn"); if($_GET['turnCount'] < $turnCount) //** Turn increased { boardUpdate($turnCount); } } //*** Place Piece *** if(isset($_GET['play'])) // turn order? player detect? { $squareID = $_GET['play']; $bid = $_GET['bid']; $Query=("SELECT turn, boardstate FROM board WHERE bid=$bid"); $Result=mysql_query($Query); $turnCount=mysql_result($Result,0,"turn"); $boardState=mysql_result($Result,0,"boardstate"); $turnCount++; $playerId = $_SESSION['char']; $Query=("SELECT p1, p2 FROM board WHERE bid=$bid"); $Result=mysql_query($Query); $p1 = mysql_result($Result,0,"p1"); $p2 = mysql_result($Result,0,"p2"); $newPiece = 0; //*default no player if($playerId == $p1) $newPiece = 1; if($playerId == $p2) $newPiece = 2; // if($newPiece != 0) // { $oldPiece = getBoardSpot($squareID, $bid); $oldLetter = $boardState{floor($squareID/3)}; $slot = $squareID%3; //***function updateCode($old, $new, $current, $slot)*** $newLetter = updateCode($oldPiece, $newPiece, $oldLetter, $slot); $newLetter = value2Letter($newLetter); $newBoard = substr_replace($boardState, $newLetter, floor($squareID/3), 1); //** Update Query for boardstate & turn $Query=("UPDATE board SET boardState = '$newBoard', turn = '$turnCount' WHERE bid = '$bid'"); mysql_query($Query); // } boardUpdate($turnCount); } function boardUpdate($turnCount) { $json = '{"turnCount":"'.$turnCount.'",'; //** turnCount ** $bid = $_GET['bid']; $Query=("SELECT boardstate FROM board WHERE bid='$bid'"); $Result=mysql_query($Query); $Board=mysql_result($Result,0,"boardstate"); $json.= '"boardState":"'.$Board.'"'; //** boardState ** $json.= '}'; echo $json; } function letter2Value($input) { if(ord($input) >= 48 && ord($input) <= 57) return ord($input) - 48; else return ord($input) - 87; } function value2Letter($input) { if($input >= 10) return chr($input += 87); else return chr($input += 48); } //*** UPDATE CODE *** updates an letter with a new peice change and returns result letter. //***** $old : peice value before update //***** $new : peice value after update //***** $current : letterValue of code before update. //***** $slot : which of the 3 sqaures the change needs to take place in. function updateCode($old, $new, $current, $slot) { if($slot == 0) {// echo $current,"+((",$new,"-",$old,")*9)"; return letter2Value($current)+(($new-$old)*9); } else if($slot == 1) {// echo $current,"+((",$new,"-",$old,")*3)"; return letter2Value($current)+(($new-$old)*3); } else //slot == 2 {// echo $current,"+((",$new,"-",$old,")"; return letter2Value($current)+($new-$old); } }//updateCode() //**** GETBOARDSPOT *** Returns the peice value at defined location on the board. //****** 0 is first sqaure increment +1 in reading order (0-254). function getBoardSpot($squareID, $bid) { $Query=("SELECT boardstate FROM board WHERE bid='$bid'"); $Result=mysql_query($Query); $Board=mysql_result($Result,0,"boardstate"); if($squareID %3 == 2) //**3rd spot** { if( letter2Value($Board{floor($squareID/3)} ) % 3 == 0) return 0; else if( letter2Value($Board{floor($squareID/3)} ) % 3 == 1) return 1; else return 2; } else if($squareID %3 == 0) //**1st spot** { if(letter2Value($Board{floor($squareID/3)} ) <= 8) return 0; else if(letter2Value($Board{floor($squareID/3)} ) >= 18) return 2; else return 1; } else //**2nd spot** { return floor(letter2Value($Board{floor($squareID/3)}))/3%3; } }//end getBoardSpot() ?> Please help, I'd be glad to provide more information if needed. Thanks in advance =)

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  • calling and killing a parent function with onmouseover and onmouseout events

    - by Zoolu
    I want to call the function upon the onmouseover="ParentFunction();" then kill it onmouseout="killParent();". Note: in my code the parent function is called initiate(); and the killer function is called reset(); which lies outside the parent function at the bottom of the script. I don't know how to kill the intitiate() function my first guess was: var reset = function(){ return initiate(); }; here's my source code: any suggestions and help appreciated. <!doctype html> <html> <head> <title> function/event prototype </title> <link rel="stylesheet" type="text/css" href="styling.css" /> </head> <body> <h2> <em>Fantastical place<br/>prototype</em> </h2> <div id="button-container"> <div id="button-box"> <button id="activate" onmouseover="initiate()" onmouseout="reset();" width="50px" height="50px" title="Activate"> </button> </div> <div id="text-box"> </div> </div> <div id="container"> <canvas id="playground" width="200px" height="250px"> </canvas> <canvas id="face" width="400px" height="200px"> </canvas> <!-- <div id="clear"> </div> --> </div> <script> alert("Welcome, there are x entries as of" +""+new Date().getHours()); //global scope var i=0; var c1 = []; //c is short for collect var c2 = []; var c3 = []; var c4 = []; var c5 = []; var c6 = []; var initiate = function(){ //the button that triggers the program var timer = setInterval(function(){clock()},90); //copy this block for ref. function clock(){ i+=1; var a = Math.round(Math.random()*200); var b = Math.round(Math.random()*250); var c = Math.round(Math.random()*200); var d = Math.round(Math.random()*250); var e = Math.round(Math.random()*200); var f = Math.round(Math.random()*250); c1.push(a); c2.push(b); c3.push(c); c4.push(d); c5.push(e); c6.push(f); // document.write(i); var c = document.getElementById("playground"); var ctx = c.getContext("2d"); ctx.beginPath(); ctx.moveTo(c3[i-2], c4[i-2]); ctx.bezierCurveTo(c1[i-2],c2[i-2],c5[i-2],c6[i-2],c3[i-1], c4[i-1]); // ctx.lineTo(c3[i-1], c4[i-1]); if(a<200){ ctx.strokeStyle="#FF33CC"; } else if(a<400){ ctx.strokeStyle="#FF33aa"; } else{ ctx.strokeStyle="#FF3388"; } ctx.stroke(); document.getElementById("text-box").innerHTML=i+"<p>Thoughts.</p>"; if(i===20){ //alert("15 reached"); clearInterval(timer);//to clearInterval must be using a global scoped variable. return; } }; //end of clock //setInterval(clock,150); var targetFace = document.getElementById("face"); var face = targetFace.getContext("2d"); var faceTimer = setInterval(function(){faceAnim()},80); //copy this block for ref. global scoped. function faceAnim(){ face.beginPath(); face.strokeStyle="#FF33CC"; face.moveTo(100,104); //eye line face.bezierCurveTo(150,125,250,125,300,104); face.moveTo(200,1); //centre line face.lineTo(200,400); face.moveTo(125,111);//left eye lid face.bezierCurveTo(160,135,170,130,185,120); face.moveTo(150,116);//left eye face.bezierCurveTo(155,125,165,125,170,118); face.moveTo(275,111);//right eye lid face.bezierCurveTo(240,135,230,130,215,120); face.moveTo(250,116);//right eye face.bezierCurveTo(245,125,235,125,230,118); face.moveTo(195, 118); //left nose face.lineTo(190, 160); face.lineTo(200,170); face.moveTo(190,160); //left nostroll face.lineTo(180,160); face.lineTo(191,154); face.moveTo(180,160); //left lower nostrol face.lineTo(200,170); face.moveTo(205, 118); //right nose face.lineTo(210, 160); face.lineTo(200,170); face.moveTo(210,160); //right nostroll face.lineTo(220,160); face.lineTo(209,154); face.moveTo(220,160); //right lower nostrol face.lineTo(200,170); face.moveTo(200,140); //outer triad face.lineTo(170, 100); face.lineTo(230, 100); face.lineTo(200, 140); face.moveTo(200,145); //outer triad drop shadow face.lineTo(170, 100); face.lineTo(230, 100); face.lineTo(200, 145); face.moveTo(200,130); //inner triad face.lineTo(180, 105); face.lineTo(220, 105); face.lineTo(200, 130); //face.lineWidth =0.6; face.moveTo(280,111);//outer right eye lid face.bezierCurveTo(240,140,230,135,210,120); face.moveTo(120,111);//outer left eye lid face.bezierCurveTo(160,140,170,135,190,120); face.moveTo(162,174); //upper mouth line face.bezierCurveTo(170,180,230,180,238,174); face.moveTo(165,175); //mouth line bottom face.bezierCurveTo(190,Math.floor(Math.random()*25+180),210,Math.floor(Math.random()*25+180),235,175); face.moveTo(232,204); //head shape face.lineTo(340, 20); face.moveTo(168,204); //head shape face.lineTo(60, 20); face.stroke(); //exicute all co-ords. }; //end of face anim var clearFace = function(){ document.getElementById('face').getContext('2d').clearRect(0, 0, 700, 750); }; setInterval(clearFace,90); }; //end of parent function var reset = function(){ document.getElementById('playground').getContext('2d').clearRect(0, 0, 700, 750); //clearInterval(faceTimer); //delete initiate(); }; </script> </body> </html>

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  • Something is making my page perform an Ajax call multiple times... [read: I've never been more frust

    - by Jack Webb-Heller
    NOTE: This is a long question. I've explained all the 'basics' at the top and then there's some further (optional) information for if you need it. Hi folks Basically last night this started happening at about 9PM whilst I was trying to restructure my code to make it a bit nicer for the designer to add a few bits to. I tried to fix it until 2AM at which point I gave up. Came back to it this morning, still baffled. I'll be honest with you, I'm a pretty bad Javascript developer. Since starting this project Javascript has been completely new to me and I've just learn as I went along. So please forgive me if my code structure is really bad (perhaps give a couple of pointers on how to improve it?). So, to the problem: to reproduce it, visit http://furnace.howcode.com (it's far from complete). This problem is a little confusing but I'd really appreciate the help. So in the second column you'll see three tabs The 'Newest' tab is selected by default. Scroll to the bottom, and 3 further results should be dynamically fetched via Ajax. Now click on the 'Top Rated' tab. You'll see all the results, but ordered by rating Scroll to the bottom of 'Top Rated'. You'll see SIX results returned. This is where it goes wrong. Only a further three should be returned (there are 18 entries in total). If you're observant you'll notice two 'blocks' of 3 returned. The first 'block' is the second page of results from the 'Newest' tab. The second block is what I just want returned. Did that make any sense? Never mind! So basically I checked this out in Firebug. What happens is, from a 'Clean' page (first load, nothing done) it calls ONE POST request to http://furnace.howcode.com/code/loadmore . But every time you load a new one of the tabs, it makes an ADDITIONAL POST request each time where there should normally only be ONE. So, can you help me? I'd really appreciate it! At this point you could start independent investigation or read on for a little further (optional) information. Thanks! Jack Further Info (may be irrelevant but here for reference): It's almost like there's some Javascript code or something being left behind that duplicates it each time. I thought it might be this code that I use to detect when the browser is scrolled to the bottom: var col = $('#col2'); col.scroll(function(){ if (col.outerHeight() == (col.get(0).scrollHeight - col.scrollTop())) loadMore(1); }); So what I thought was that code was left behind, and so every time you scroll #col2 (which contains different data for each tab) it detected that and added it for #newest as well. So, I made each tab click give #col2 a dynamic class - either .newestcol, .featuredcol, or .topratedcol. And then I changed the var col=$('.newestcol');dynamically so it would only detect it individually for each tab (makin' any sense?!). But hey, that didn't do anything. Another useful tidbit: here's the PHP for http://furnace.howcode.com/code/loadmore: $kind = $this->input->post('kind'); if ($kind == 1){ // kind is 1 - newest $start = $this->input->post('currentpage'); $data['query'] = "SELECT code.id AS codeid, code.title AS codetitle, code.summary AS codesummary, code.author AS codeauthor, code.rating AS rating, code.date, code_tags.*, tags.*, users.firstname AS authorname, users.id AS authorid, GROUP_CONCAT(tags.tag SEPARATOR ', ') AS taggroup FROM code, code_tags, tags, users WHERE users.id = code.author AND code_tags.code_id = code.id AND tags.id = code_tags.tag_id GROUP BY code_id ORDER BY date DESC LIMIT $start, 15 "; $this->load->view('code/ajaxlist',$data); } elseif ($kind == 2) { // kind is 2 - featured So my jQuery code sends a variable 'kind'. If it's 1, it runs the query for Newest, etc. etc. The PHP code for furnace.howcode.com/code/ajaxlist is: <?php // Our query base // SELECT * FROM code ORDER BY date DESC $query = $this->db->query($query); foreach($query->result() as $row) { ?> <script type="text/javascript"> $('#title-<?php echo $row->codeid;?>').click(function() { var form_data = { id: <?php echo $row->codeid; ?> }; $('#col3').fadeOut('slow', function() { $.ajax({ url: "<?php echo site_url('code/viewajax');?>", type: 'POST', data: form_data, success: function(msg) { $('#col3').html(msg); $('#col3').fadeIn('fast'); } }); }); }); </script> <div class="result"> <div class="resulttext"> <div id="title-<?php echo $row->codeid; ?>" class="title"> <?php echo anchor('#',$row->codetitle); ?> </div> <div class="summary"> <?php echo $row->codesummary; ?> </div> <!-- Now insert the 5-star rating system --> <?php include($_SERVER['DOCUMENT_ROOT']."/fivestars/5star.php");?> <div class="bottom"> <div class="author"> Submitted by <?php echo anchor('auth/profile/'.$row->authorid,''.$row->authorname);?> </div> <?php // Now we need to take the GROUP_CONCATted tags and split them using the magic of PHP into seperate tags $tagarray = explode(", ", $row->taggroup); foreach ($tagarray as $tag) { ?> <div class="tagbutton" href="#"> <span><?php echo $tag; ?></span> </div> <?php } ?> </div> </div> </div> <?php } echo "&nbsp;";?> <script type="text/javascript"> var newpage = <?php echo $this->input->post('currentpage') + 15;?>; </script> So that's everything in PHP. The rest you should be able to view with Firebug or by viewing the Source code. I've put all the Tab/clicking/Ajaxloading bits in the tags at the very bottom. There's a comment before it all kicks off. Thanks so much for your help!

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  • Scala parser combinator runs out of memory

    - by user3217013
    I wrote the following parser in Scala using the parser combinators: import scala.util.parsing.combinator._ import scala.collection.Map import scala.io.StdIn object Keywords { val Define = "define" val True = "true" val False = "false" val If = "if" val Then = "then" val Else = "else" val Return = "return" val Pass = "pass" val Conj = ";" val OpenParen = "(" val CloseParen = ")" val OpenBrack = "{" val CloseBrack = "}" val Comma = "," val Plus = "+" val Minus = "-" val Times = "*" val Divide = "/" val Pow = "**" val And = "&&" val Or = "||" val Xor = "^^" val Not = "!" val Equals = "==" val NotEquals = "!=" val Assignment = "=" } //--------------------------------------------------------------------------------- sealed abstract class Op case object Plus extends Op case object Minus extends Op case object Times extends Op case object Divide extends Op case object Pow extends Op case object And extends Op case object Or extends Op case object Xor extends Op case object Not extends Op case object Equals extends Op case object NotEquals extends Op case object Assignment extends Op //--------------------------------------------------------------------------------- sealed abstract class Term case object TrueTerm extends Term case object FalseTerm extends Term case class FloatTerm(value : Float) extends Term case class StringTerm(value : String) extends Term case class Identifier(name : String) extends Term //--------------------------------------------------------------------------------- sealed abstract class Expression case class TermExp(term : Term) extends Expression case class UnaryOp(op : Op, exp : Expression) extends Expression case class BinaryOp(op : Op, left : Expression, right : Expression) extends Expression case class FuncApp(funcName : Term, args : List[Expression]) extends Expression //--------------------------------------------------------------------------------- sealed abstract class Statement case class ExpressionStatement(exp : Expression) extends Statement case class Pass() extends Statement case class Return(value : Expression) extends Statement case class AssignmentVar(variable : Term, exp : Expression) extends Statement case class IfThenElse(testBody : Expression, thenBody : Statement, elseBody : Statement) extends Statement case class Conjunction(left : Statement, right : Statement) extends Statement case class AssignmentFunc(functionName : Term, args : List[Term], body : Statement) extends Statement //--------------------------------------------------------------------------------- class myParser extends JavaTokenParsers { val keywordMap : Map[String, Op] = Map( Keywords.Plus -> Plus, Keywords.Minus -> Minus, Keywords.Times -> Times, Keywords.Divide -> Divide, Keywords.Pow -> Pow, Keywords.And -> And, Keywords.Or -> Or, Keywords.Xor -> Xor, Keywords.Not -> Not, Keywords.Equals -> Equals, Keywords.NotEquals -> NotEquals, Keywords.Assignment -> Assignment ) def floatTerm : Parser[Term] = decimalNumber ^^ { case x => FloatTerm( x.toFloat ) } def stringTerm : Parser[Term] = stringLiteral ^^ { case str => StringTerm(str) } def identifier : Parser[Term] = ident ^^ { case value => Identifier(value) } def boolTerm : Parser[Term] = (Keywords.True | Keywords.False) ^^ { case Keywords.True => TrueTerm case Keywords.False => FalseTerm } def simpleTerm : Parser[Expression] = (boolTerm | floatTerm | stringTerm) ^^ { case term => TermExp(term) } def argument = expression def arguments_aux : Parser[List[Expression]] = (argument <~ Keywords.Comma) ~ arguments ^^ { case arg ~ argList => arg :: argList } def arguments = arguments_aux | { argument ^^ { case arg => List(arg) } } def funcAppArgs : Parser[List[Expression]] = funcEmptyArgs | ( Keywords.OpenParen ~> arguments <~ Keywords.CloseParen ^^ { case args => args.foldRight(List[Expression]()) ( (a,b) => a :: b ) } ) def funcApp = identifier ~ funcAppArgs ^^ { case funcName ~ argList => FuncApp(funcName, argList) } def variableTerm : Parser[Expression] = identifier ^^ { case name => TermExp(name) } def atomic_expression = simpleTerm | funcApp | variableTerm def paren_expression : Parser[Expression] = Keywords.OpenParen ~> expression <~ Keywords.CloseParen def unary_operation : Parser[String] = Keywords.Not def unary_expression : Parser[Expression] = operation(0) ~ expression(0) ^^ { case op ~ exp => UnaryOp(keywordMap(op), exp) } def operation(precedence : Int) : Parser[String] = precedence match { case 0 => Keywords.Not case 1 => Keywords.Pow case 2 => Keywords.Times | Keywords.Divide | Keywords.And case 3 => Keywords.Plus | Keywords.Minus | Keywords.Or | Keywords.Xor case 4 => Keywords.Equals | Keywords.NotEquals case _ => throw new Exception("No operations with this precedence.") } def binary_expression(precedence : Int) : Parser[Expression] = precedence match { case 0 => throw new Exception("No operation with zero precedence.") case n => (expression (n-1)) ~ operation(n) ~ (expression (n)) ^^ { case left ~ op ~ right => BinaryOp(keywordMap(op), left, right) } } def expression(precedence : Int) : Parser[Expression] = precedence match { case 0 => unary_expression | paren_expression | atomic_expression case n => binary_expression(n) | expression(n-1) } def expression : Parser[Expression] = expression(4) def expressionStmt : Parser[Statement] = expression ^^ { case exp => ExpressionStatement(exp) } def assignment : Parser[Statement] = (identifier <~ Keywords.Assignment) ~ expression ^^ { case varName ~ exp => AssignmentVar(varName, exp) } def ifthen : Parser[Statement] = ((Keywords.If ~ Keywords.OpenParen) ~> expression <~ Keywords.CloseParen) ~ ((Keywords.Then ~ Keywords.OpenBrack) ~> statements <~ Keywords.CloseBrack) ^^ { case ifBody ~ thenBody => IfThenElse(ifBody, thenBody, Pass()) } def ifthenelse : Parser[Statement] = ((Keywords.If ~ Keywords.OpenParen) ~> expression <~ Keywords.CloseParen) ~ ((Keywords.Then ~ Keywords.OpenBrack) ~> statements <~ Keywords.CloseBrack) ~ ((Keywords.Else ~ Keywords.OpenBrack) ~> statements <~ Keywords.CloseBrack) ^^ { case ifBody ~ thenBody ~ elseBody => IfThenElse(ifBody, thenBody, elseBody) } def pass : Parser[Statement] = Keywords.Pass ^^^ { Pass() } def returnStmt : Parser[Statement] = Keywords.Return ~> expression ^^ { case exp => Return(exp) } def statement : Parser[Statement] = ((pass | returnStmt | assignment | expressionStmt) <~ Keywords.Conj) | ifthenelse | ifthen def statements_aux : Parser[Statement] = statement ~ statements ^^ { case st ~ sts => Conjunction(st, sts) } def statements : Parser[Statement] = statements_aux | statement def funcDefBody : Parser[Statement] = Keywords.OpenBrack ~> statements <~ Keywords.CloseBrack def funcEmptyArgs = Keywords.OpenParen ~ Keywords.CloseParen ^^^ { List() } def funcDefArgs : Parser[List[Term]] = funcEmptyArgs | Keywords.OpenParen ~> repsep(identifier, Keywords.Comma) <~ Keywords.CloseParen ^^ { case args => args.foldRight(List[Term]()) ( (a,b) => a :: b ) } def funcDef : Parser[Statement] = (Keywords.Define ~> identifier) ~ funcDefArgs ~ funcDefBody ^^ { case funcName ~ funcArgs ~ body => AssignmentFunc(funcName, funcArgs, body) } def funcDefAndStatement : Parser[Statement] = funcDef | statement def funcDefAndStatements_aux : Parser[Statement] = funcDefAndStatement ~ funcDefAndStatements ^^ { case stmt ~ stmts => Conjunction(stmt, stmts) } def funcDefAndStatements : Parser[Statement] = funcDefAndStatements_aux | funcDefAndStatement def parseProgram : Parser[Statement] = funcDefAndStatements def eval(input : String) = { parseAll(parseProgram, input) match { case Success(result, _) => result case Failure(m, _) => println(m) case _ => println("") } } } object Parser { def main(args : Array[String]) { val x : myParser = new myParser() println(args(0)) val lines = scala.io.Source.fromFile(args(0)).mkString println(x.eval(lines)) } } The problem is, when I run the parser on the following example it works fine: define foo(a) { if (!h(IM) && a) then { return 0; } if (a() && !h()) then { return 0; } } But when I add threes characters in the first if statement, it runs out of memory. This is absolutely blowing my mind. Can anyone help? (I suspect it has to do with repsep, but I am not sure.) define foo(a) { if (!h(IM) && a(1)) then { return 0; } if (a() && !h()) then { return 0; } } EDIT: Any constructive comments about my Scala style is also appreciated.

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  • datalist edit mode.

    - by Ranjana
    i have a datalist control <ItemTemplate> <tr> <td height="31px"> <asp:Label ID="lblStudentName" runat="server" Text="StudentName :" Font-Bold="true"></asp:Label> <%# DataBinder.Eval(Container.DataItem, "StudentName") %> </td> <td height="31px"> <asp:LinkButton ID="lnkEdit" runat="server" CommandName="edit">Edit</asp:LinkButton> </td> </tr> <tr> <td> <asp:Label ID="lblAdmissionNo" runat="server" Text="AdmissionNo :" Font-Bold="true"></asp:Label> <%# DataBinder.Eval(Container.DataItem, "AdmissionNo")%> </td> </tr> <tr> <td height="31px"> <asp:Label ID="lblStudentRollNo" runat="server" Text="StdentRollNo :" Font-Bold="true"></asp:Label> <%# DataBinder.Eval(Container.DataItem, "StdentRollNo") %> </td> <td height="31px"> <asp:LinkButton ID="lnkEditroll" runat="server" CommandName="edit">Edit</asp:LinkButton> </td> </tr> </ItemTemplate> <EditItemTemplate> <tr> <td height="31px"> <asp:Label ID="lblStudentName" runat="server" Text="StudentName :" Font-Bold="true"></asp:Label> <asp:TextBox ID="txtProductName" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "StudentName") %>'></asp:TextBox> </td> <td> <asp:LinkButton ID="lnkUpdate" runat="server" CommandName="update">Update</asp:LinkButton> <asp:LinkButton ID="lnkCancel" runat="server" CommandName="cancel">Cancel</asp:LinkButton> </td> </tr> <tr> <td height="31px"> <asp:Label ID="lblAdmissionNo" runat="server" Text="AdmissionNo :" Font-Bold="true"></asp:Label> <%# DataBinder.Eval(Container.DataItem, "AdmissionNo")%> </td> </tr> <tr> <td height="31px"> <asp:Label ID="lblStudentRollNo" runat="server" Text="StudentRollNo :" Font-Bold="true"></asp:Label> <asp:TextBox ID="txtStudentRollNo" runat="server" Text='<%# DataBinder.Eval(Container.DataItem, "StdentRollNo") %>'></asp:TextBox> </td> <td> <asp:LinkButton ID="LinkButton1" runat="server" CommandName="update">Update</asp:LinkButton> <asp:LinkButton ID="LinkButton2" runat="server" CommandName="cancel">Cancel</asp:LinkButton> </td> </tr> </EditItemTemplate> <FooterTemplate> </table> </FooterTemplate> </asp:DataList> code behind: protected void Page_Load(object sender, EventArgs e) { if (!Page.IsPostBack) { DataTable dt = new DataTable(); dt = obj.GetSamples(); DataList1.DataSource = dt; DataList1.DataBind(); } } public void DataBind() { DataTable dt = new DataTable(); dt = obj.GetSamples(); DataList1.DataSource = dt; DataList1.DataBind(); } protected void DataList1_EditCommand1(object source, DataListCommandEventArgs e) { DataList1.EditItemIndex = e.Item.ItemIndex; DataBind(); } protected void DataList1_CancelCommand1(object source, DataListCommandEventArgs e) { DataList1.EditItemIndex = -1; DataBind(); } protected void DataList1_UpdateCommand1(object source, DataListCommandEventArgs e) { // Get the DataKey value associated with current Item Index. // int AdmissionNo = Convert.ToInt32(DataList1.DataKeys[e.Item.ItemIndex]); string AdmissionNo = DataList1.DataKeys[e.Item.ItemIndex].ToString(); // Get updated value entered by user in textbox control for // ProductName field. TextBox txtProductName; txtProductName = (TextBox)e.Item.FindControl("txtProductName"); TextBox txtStudentRollNo; txtStudentRollNo = (TextBox)e.Item.FindControl("txtStudentRollNo"); // string variable to store the connection string // retrieved from the connectionStrings section of web.config string connectionString = ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString; // sql connection object SqlConnection mySqlConnection = new SqlConnection(connectionString); // sql command object initialized with update command text SqlCommand mySqlCommand = new SqlCommand("update SchoolAdmissionForm set StudentName=@studentname ,StdentRollNo=@studentroll where AdmissionNo=@admissionno", mySqlConnection); mySqlCommand.Parameters.Add("@studentname", SqlDbType.VarChar).Value = txtProductName.Text; mySqlCommand.Parameters.Add("@admissionno", SqlDbType.VarChar).Value = AdmissionNo; mySqlCommand.Parameters.Add("@studentroll", SqlDbType.VarChar).Value = txtStudentRollNo.Text; // check the connection state and open it accordingly. if (mySqlConnection.State == ConnectionState.Closed) mySqlConnection.Open(); // execute sql update query mySqlCommand.ExecuteNonQuery(); // check the connection state and close it accordingly. if (mySqlConnection.State == ConnectionState.Open) mySqlConnection.Close(); // reset the DataList mode back to its initial state DataList1.EditItemIndex = -1; DataBind(); // BindDataList(); } But it works fine.... but when i click edit command both the Fields 1.StudentName 2.StudentRollNo im getting textboxes to all the fields where i placed textbox when i click 'edit' command and not the particular field alone . but i should get oly the textbox visible to the field to which i clik as 'edit' , and the rest remain same without showing textboxes even though it is in editmode

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  • PHP Form: After getting results adding a new table row when entering new information.

    - by Chris
    Hello, Although probarly quite simple, i cannot seem to find the following. The form takes certain data, and then represents the data in a table. Next step i click the hyperlink that takes me back to the form. Now my question is how exactly do i make it possible when filling in the same form again so both results are displayed in the same table? Then filling in a other form with data adds another row and so on. Regards. The code below (pardon me that it is not english). <?php session_start(); ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-Strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title>ExpoFormulier</title> <body> <?php if (!empty($_POST)) { $standnaam = $_POST["standnaam"]; $oppervlakte = $_POST["oppervlakte"]; //value in the form van checkboxes op 1 zetten! $verdieping = isset($_POST["verdieping"]) ? $_POST["verdieping"] : 0; //if checkbox checked value 1 anders 0 $telefoon = isset($_POST["telefoon"]) ? $_POST["telefoon"] : 0; $netwerk = isset($_POST["netwerk"]) ? $_POST["netwerk"] : 0; if (is_numeric($oppervlakte)) { $_SESSION["standnaam"]=$standnaam; $_SESSION["oppervlakte"]=$oppervlakte; $_SESSION["verdieping"]=$verdieping; $_SESSION["telefoon"]=$telefoon; $_SESSION["netwerk"]=$netwerk; header("Location:ExpoOverzicht.php"); //verzenden naar ExpoOverzicht.php dmv header } else { echo "<h1>Foute gegevens, Opnieuw invullen a.u.b</h1>"; } } ?> <form action="<?php echo $_SERVER["PHP_SELF"]; ?>" method="post" id="form1"> <h1>Vul de gegevens in</h1> <table> <tr> <td>Standnaam:</td> <td><input type="text" name="standnaam" size="18"/></td> </tr> <tr> <td>Oppervlakte (in m^2):</td> <td><input type="text" name="oppervlakte" size="6"/></td> </tr> <tr> <td>Verdieping:</td> <td><input type="checkbox" name="verdieping" value="1"/></td> <!--value op 1 zetten voor checkbox! indien checked is value 1 --> </tr> <tr> <td>Telefoon:</td> <td><input type="checkbox" name="telefoon" value="1"/></td> </tr> <tr> <td>Netwerk:</td> <td><input type="checkbox" name="netwerk" value="1"/></td> </tr> <tr> <td><input type="submit" name="verzenden" value="Verzenden"/></td> </tr> </table> </form> Second File: <?php session_start(); ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-Strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title>ExpoOverzicht</title> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <link href="StyleSheetExpo.css" rel="stylesheet" type="text/css" /> </head> <body> <h1>Overzicht van de ingegeven standen in deze sessie</h1> <?php $standnaam = $_SESSION["standnaam"]; $oppervlakte = $_SESSION["oppervlakte"]; $verdieping = $_SESSION["verdieping"]; $telefoon = $_SESSION["telefoon"]; $netwerk = $_SESSION["netwerk"]; $result1 = 0; //telkens declaren anders fout "undefined variable" $result2 = 0; $result3 = 0; $prijsCom = 0; $prijsVerdieping = 0; for ($i=1; $i <= $oppervlakte; $i++) { if($i <= 10) { $tarief1 = 1 * 100; $result1 += $tarief1; } if($i > 10 && $i <= 30) { $tarief2 = 1 * 90; $result2 += $tarief2; } if($i > 30) { $tarief3 = 1 * 80; $result3 += $tarief3; } } $prijsOpp = $result1 + $result2 + $result3; if($verdieping == 1) { $prijsVerdieping = $oppervlakte * 120; } if(($telefoon == 1) || ($netwerk == 1)) // eerst deze OR conditie of anders gebruikt de code alleen nog maar 20 { $prijsCom = 20; } if(($telefoon == 1) && ($netwerk == 1)) { $prijsCom = 30; } $totalePrijs = $prijsOpp + $prijsVerdieping + $prijsCom; echo "<table class=\"tableExpo\">"; echo "<th>Standnaam</th>"; echo "<th>Oppervlakte</th>"; echo "<th>Verdieping</th>"; echo "<th>Telefoon</th>"; echo "<th>Netwerk</th>"; echo "<th>Totale prijs</th>"; echo "<tr>"; echo "<td>".$standnaam."</td>"; echo "<td>".$oppervlakte."</td>"; echo "<td>".$verdieping."</td>"; echo "<td>".$telefoon."</td>"; echo "<td>".$netwerk."</td>"; echo "<td>".$totalePrijs."</td>"; echo "</tr>"; echo "</table>"; ?> <a href="ExpoFormulier.php">Terug naar het formulier</a> </body> </html> </body> </html>

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  • Problems with inheritance query view and one to many association in entity framework 4

    - by Kazys
    Hi, I have situation in with I stucked and don't know way out. The problem is in my bigger model, but I have made small example which shows the same problem. I have 4 tables. I called them SuperParent, NamedParent, TypedParent and ParentType. NamedParent and TypedParent derives from superParent. TypedParent has one to many association with ParentType. I describe mapping for entities using queryView. The problem is then I want to get TypedParents and Include ParentType I get the following exception: An error occurred while preparing the command definition. See the inner exception for details. --- System.ArgumentException: The ResultType of the specified expression is not compatible with the required type. The expression ResultType is 'Transient.reference[PasibandymaiModel.SuperParent]' but the required type is 'Transient.reference[PasibandymaiModel.TypedParent]'. Parameter name: arguments[1] To get TypedParents I use following code: context.SuperParent.OfType().Include("ParentType"); my edmx file: <edmx:Edmx Version="2.0" xmlns:edmx="http://schemas.microsoft.com/ado/2008/10/edmx"> <!-- EF Runtime content --> <edmx:Runtime> <!-- SSDL content --> <edmx:StorageModels> <Schema Namespace="PasibandymaiModel.Store" Alias="Self" Provider="System.Data.SqlClient" ProviderManifestToken="2005" xmlns:store="http://schemas.microsoft.com/ado/2007/12/edm/EntityStoreSchemaGenerator" xmlns="http://schemas.microsoft.com/ado/2009/02/edm/ssdl"> <EntityContainer Name="PasibandymaiModelStoreContainer"> <EntitySet Name="NamedParent" EntityType="PasibandymaiModel.Store.NamedParent" store:Type="Tables" Schema="dbo" /> <EntitySet Name="ParentType" EntityType="PasibandymaiModel.Store.ParentType" store:Type="Tables" Schema="dbo" /> <EntitySet Name="SuperParent" EntityType="PasibandymaiModel.Store.SuperParent" store:Type="Tables" Schema="dbo" /> <EntitySet Name="TypedParent" EntityType="PasibandymaiModel.Store.TypedParent" store:Type="Tables" Schema="dbo" /> <AssociationSet Name="fk_NamedParent_SuperParent" Association="PasibandymaiModel.Store.fk_NamedParent_SuperParent"> <End Role="SuperParent" EntitySet="SuperParent" /> <End Role="NamedParent" EntitySet="NamedParent" /> </AssociationSet> <AssociationSet Name="fk_TypedParent_ParentType" Association="PasibandymaiModel.Store.fk_TypedParent_ParentType"> <End Role="ParentType" EntitySet="ParentType" /> <End Role="TypedParent" EntitySet="TypedParent" /> </AssociationSet> <AssociationSet Name="fk_TypedParent_SuperParent" Association="PasibandymaiModel.Store.fk_TypedParent_SuperParent"> <End Role="SuperParent" EntitySet="SuperParent" /> <End Role="TypedParent" EntitySet="TypedParent" /> </AssociationSet> </EntityContainer> <EntityType Name="NamedParent"> <Key> <PropertyRef Name="ParentId" /> </Key> <Property Name="ParentId" Type="int" Nullable="false" /> <Property Name="Name" Type="nvarchar" Nullable="false" MaxLength="100" /> </EntityType> <EntityType Name="ParentType"> <Key> <PropertyRef Name="ParentTypeId" /> </Key> <Property Name="ParentTypeId" Type="int" Nullable="false" StoreGeneratedPattern="Identity" /> <Property Name="Name" Type="nvarchar" MaxLength="100" /> </EntityType> <EntityType Name="SuperParent"> <Key> <PropertyRef Name="ParentId" /> </Key> <Property Name="ParentId" Type="int" Nullable="false" StoreGeneratedPattern="Identity" /> <Property Name="SomeAttribute" Type="nvarchar" Nullable="false" MaxLength="100" /> </EntityType> <EntityType Name="TypedParent"> <Key> <PropertyRef Name="ParentId" /> </Key> <Property Name="ParentId" Type="int" Nullable="false" /> <Property Name="ParentTypeId" Type="int" Nullable="false"/> </EntityType> <Association Name="fk_NamedParent_SuperParent"> <End Role="SuperParent" Type="PasibandymaiModel.Store.SuperParent" Multiplicity="1" /> <End Role="NamedParent" Type="PasibandymaiModel.Store.NamedParent" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="SuperParent"> <PropertyRef Name="ParentId" /> </Principal> <Dependent Role="NamedParent"> <PropertyRef Name="ParentId" /> </Dependent> </ReferentialConstraint> </Association> <Association Name="fk_TypedParent_ParentType"> <End Role="ParentType" Type="PasibandymaiModel.Store.ParentType" Multiplicity="1" /> <End Role="TypedParent" Type="PasibandymaiModel.Store.TypedParent" Multiplicity="*" /> <ReferentialConstraint> <Principal Role="ParentType"> <PropertyRef Name="ParentTypeId" /> </Principal> <Dependent Role="TypedParent"> <PropertyRef Name="ParentTypeId" /> </Dependent> </ReferentialConstraint> </Association> <Association Name="fk_TypedParent_SuperParent"> <End Role="SuperParent" Type="PasibandymaiModel.Store.SuperParent" Multiplicity="1" /> <End Role="TypedParent" Type="PasibandymaiModel.Store.TypedParent" Multiplicity="0..1" /> <ReferentialConstraint> <Principal Role="SuperParent"> <PropertyRef Name="ParentId" /> </Principal> <Dependent Role="TypedParent"> <PropertyRef Name="ParentId" /> </Dependent> </ReferentialConstraint> </Association> <Function Name="ChildDelete" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ChildId" Type="int" Mode="In" /> </Function> <Function Name="ChildInsert" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="Name" Type="nvarchar" Mode="In" /> <Parameter Name="ParentId" Type="int" Mode="In" /> </Function> <Function Name="ChildUpdate" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ChildId" Type="int" Mode="In" /> <Parameter Name="ParentId" Type="int" Mode="In" /> <Parameter Name="Name" Type="nvarchar" Mode="In" /> </Function> <Function Name="NamedParentDelete" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentId" Type="int" Mode="In" /> </Function> <Function Name="NamedParentInsert" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="Name" Type="nvarchar" Mode="In" /> <Parameter Name="SomeAttribute" Type="nvarchar" Mode="In" /> </Function> <Function Name="NamedParentUpdate" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentId" Type="int" Mode="In" /> <Parameter Name="SomeAttribute" Type="nvarchar" Mode="In" /> <Parameter Name="Name" Type="nvarchar" Mode="In" /> </Function> <Function Name="ParentTypeDelete" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentTypeId" Type="int" Mode="In" /> </Function> <Function Name="ParentTypeInsert" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="Name" Type="nvarchar" Mode="In" /> </Function> <Function Name="ParentTypeUpdate" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentTypeId" Type="int" Mode="In" /> <Parameter Name="Name" Type="nvarchar" Mode="In" /> </Function> <Function Name="TypedParentDelete" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentId" Type="int" Mode="In" /> </Function> <Function Name="TypedParentInsert" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentTypeId" Type="int" Mode="In" /> <Parameter Name="SomeAttribute" Type="nvarchar" Mode="In" /> </Function> <Function Name="TypedParentUpdate" Aggregate="false" BuiltIn="false" NiladicFunction="false" IsComposable="false" ParameterTypeSemantics="AllowImplicitConversion" Schema="dbo"> <Parameter Name="ParentId" Type="int" Mode="In" /> <Parameter Name="SomeAttribute" Type="nvarchar" Mode="In" /> <Parameter Name="ParentTypeId" Type="int" Mode="In" /> </Function> </Schema> </edmx:StorageModels> <!-- CSDL content --> <edmx:ConceptualModels> <Schema Namespace="PasibandymaiModel" Alias="Self" xmlns:annotation="http://schemas.microsoft.com/ado/2009/02/edm/annotation" xmlns="http://schemas.microsoft.com/ado/2008/09/edm"> <EntityContainer Name="PasibandymaiEntities" annotation:LazyLoadingEnabled="true"> <EntitySet Name="ParentType" EntityType="PasibandymaiModel.ParentType" /> <EntitySet Name="SuperParent" EntityType="PasibandymaiModel.SuperParent" /> <AssociationSet Name="ParentTypeTypedParent" Association="PasibandymaiModel.ParentTypeTypedParent"> <End Role="ParentType" EntitySet="ParentType" /> <End Role="TypedParent" EntitySet="SuperParent" /> </AssociationSet> </EntityContainer> <EntityType Name="NamedParent" BaseType="PasibandymaiModel.SuperParent"> <Property Type="String" Name="Name" Nullable="false" MaxLength="100" FixedLength="false" Unicode="true" /> </EntityType> <EntityType Name="ParentType"> <Key> <PropertyRef Name="ParentTypeId" /> </Key> <Property Type="Int32" Name="ParentTypeId" Nullable="false" annotation:StoreGeneratedPattern="Identity" /> <Property Type="String" Name="Name" MaxLength="100" FixedLength="false" Unicode="true" /> <NavigationProperty Name="TypedParent" Relationship="PasibandymaiModel.ParentTypeTypedParent" FromRole="ParentType" ToRole="TypedParent" /> </EntityType> <EntityType Name="SuperParent" Abstract="true"> <Key> <PropertyRef Name="ParentId" /> </Key> <Property Type="Int32" Name="ParentId" Nullable="false" annotation:StoreGeneratedPattern="Identity" /> <Property Type="String" Name="SomeAttribute" Nullable="false" MaxLength="100" FixedLength="false" Unicode="true" /> </EntityType> <EntityType Name="TypedParent" BaseType="PasibandymaiModel.SuperParent"> <NavigationProperty Name="ParentType" Relationship="PasibandymaiModel.ParentTypeTypedParent" FromRole="TypedParent" ToRole="ParentType" /> <Property Type="Int32" Name="ParentTypeId" Nullable="false" /> </EntityType> <Association Name="ParentTypeTypedParent"> <End Type="PasibandymaiModel.ParentType" Role="ParentType" Multiplicity="1" /> <End Type="PasibandymaiModel.TypedParent" Role="TypedParent" Multiplicity="*" /> <ReferentialConstraint> <Principal Role="ParentType"> <PropertyRef Name="ParentTypeId" /> </Principal> <Dependent Role="TypedParent"> <PropertyRef Name="ParentTypeId" /> </Dependent> </ReferentialConstraint> </Association> </Schema> </edmx:ConceptualModels> <!-- C-S mapping content --> <edmx:Mappings> <Mapping Space="C-S" xmlns="http://schemas.microsoft.com/ado/2008/09/mapping/cs"> <EntityContainerMapping StorageEntityContainer="PasibandymaiModelStoreContainer" CdmEntityContainer="PasibandymaiEntities"> <EntitySetMapping Name="ParentType"> <QueryView> SELECT VALUE PasibandymaiModel.ParentType(tp.ParentTypeId, tp.Name) FROM PasibandymaiModelStoreContainer.ParentType AS tp </QueryView> </EntitySetMapping> <EntitySetMapping Name="SuperParent"> <QueryView> SELECT VALUE CASE WHEN (np.ParentId IS NOT NULL) THEN PasibandymaiModel.NamedParent(sp.ParentId, sp.SomeAttribute, np.Name) WHEN (tp.ParentId IS NOT NULL) THEN PasibandymaiModel.TypedParent(sp.ParentId, sp.SomeAttribute, tp.ParentTypeId) END FROM PasibandymaiModelStoreContainer.SuperParent AS sp LEFT JOIN PasibandymaiModelStoreContainer.NamedParent AS np ON sp.ParentId = np.ParentId LEFT JOIN PasibandymaiModelStoreContainer.TypedParent AS tp ON sp.ParentId = tp.ParentId </QueryView> <QueryView TypeName="PasibandymaiModel.TypedParent"> SELECT VALUE PasibandymaiModel.TypedParent(sp.ParentId, sp.SomeAttribute, tp.ParentTypeId) FROM PasibandymaiModelStoreContainer.SuperParent AS sp INNER JOIN PasibandymaiModelStoreContainer.TypedParent AS tp ON sp.ParentId = tp.ParentId </QueryView> <QueryView TypeName="PasibandymaiModel.NamedParent"> SELECT VALUE PasibandymaiModel.NamedParent(sp.ParentId, sp.SomeAttribute, np.Name) FROM PasibandymaiModelStoreContainer.SuperParent AS sp INNER JOIN PasibandymaiModelStoreContainer.NamedParent AS np ON sp.ParentId = np.ParentId </QueryView> </EntitySetMapping> </EntityContainerMapping> </Mapping> </edmx:Mappings> </edmx:Runtime> </edmx:Edmx> I have tried using AssociationSetMapping instead of using Association with ReferentialConstraint. But then couldn't insert related entities at once, becouse entity framework didn't provided entity key of inserted entities for related entities. Thanks for any idea

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  • How to know if the client has terminated in sockets

    - by shadyabhi
    Suppose, I have a connected socket after writing this code.. if ((sd = accept(socket_d, (struct sockaddr *)&client_addr, &alen)) < 0) { perror("accept failed\n"); exit(1); } How can I know at the server side that client has exited. My whole program actually does the following.. Accepts a connection from client Starts a new thread that reads messages from that particular client and then broadcast this message to all the connected clients. If you want to see the whole code... In this whole code. I am also struggling with one more problem that whenever I kill a client with Ctrl+C, my server terminates abruptly.. It would be nice if anyone could suggest what the problem is.. #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <signal.h> #include <errno.h> #include <pthread.h> /*CONSTANTS*/ #define DEFAULT_PORT 10000 #define LISTEN_QUEUE_LIMIT 6 #define TOTAL_CLIENTS 10 #define CHAR_BUFFER 256 /*GLOBAL VARIABLE*/ int current_client = 0; int connected_clients[TOTAL_CLIENTS]; extern int errno; void *client_handler(void * socket_d); int main(int argc, char *argv[]) { struct sockaddr_in server_addr;/* structure to hold server's address*/ int socket_d; /* listening socket descriptor */ int port; /* protocol port number */ int option_value; /* needed for setsockopt */ pthread_t tid[TOTAL_CLIENTS]; port = (argc > 1)?atoi(argv[1]):DEFAULT_PORT; /* Socket Server address structure */ memset((char *)&server_addr, 0, sizeof(server_addr)); server_addr.sin_family = AF_INET; /* set family to Internet */ server_addr.sin_addr.s_addr = INADDR_ANY; /* set the local IP address */ server_addr.sin_port = htons((u_short)port); /* Set port */ /* Create socket */ if ( (socket_d = socket(PF_INET, SOCK_STREAM, 0)) < 0) { fprintf(stderr, "socket creation failed\n"); exit(1); } /* Make listening socket's port reusable */ if (setsockopt(socket_d, SOL_SOCKET, SO_REUSEADDR, (char *)&option_value, sizeof(option_value)) < 0) { fprintf(stderr, "setsockopt failure\n"); exit(1); } /* Bind a local address to the socket */ if (bind(socket_d, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) { fprintf(stderr, "bind failed\n"); exit(1); } /* Specify size of request queue */ if (listen(socket_d, LISTEN_QUEUE_LIMIT) < 0) { fprintf(stderr, "listen failed\n"); exit(1); } memset(connected_clients,0,sizeof(int)*TOTAL_CLIENTS); for (;;) { struct sockaddr_in client_addr; /* structure to hold client's address*/ int alen = sizeof(client_addr); /* length of address */ int sd; /* connected socket descriptor */ if ((sd = accept(socket_d, (struct sockaddr *)&client_addr, &alen)) < 0) { perror("accept failed\n"); exit(1); } else printf("\n I got a connection from (%s , %d)\n",inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port)); if (pthread_create(&tid[current_client],NULL,(void *)client_handler,(void *)sd) != 0) { perror("pthread_create error"); continue; } connected_clients[current_client]=sd; current_client++; /*Incrementing Client number*/ } return 0; } void *client_handler(void *connected_socket) { int sd; sd = (int)connected_socket; for ( ; ; ) { ssize_t n; char buffer[CHAR_BUFFER]; for ( ; ; ) { if (n = read(sd, buffer, sizeof(char)*CHAR_BUFFER) == -1) { perror("Error reading from client"); pthread_exit(1); } int i=0; for (i=0;i<current_client;i++) { if (write(connected_clients[i],buffer,sizeof(char)*CHAR_BUFFER) == -1) perror("Error sending messages to a client while multicasting"); } } } } My client side is this (Maye be irrelevant while answering my question) #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> #include <string.h> #include <stdlib.h> void error(char *msg) { perror(msg); exit(0); } void *listen_for_message(void * fd) { int sockfd = (int)fd; int n; char buffer[256]; bzero(buffer,256); printf("YOUR MESSAGE: "); fflush(stdout); while (1) { n = read(sockfd,buffer,256); if (n < 0) error("ERROR reading from socket"); if (n == 0) pthread_exit(1); printf("\nMESSAGE BROADCAST: %sYOUR MESSAGE: ",buffer); fflush(stdout); } } int main(int argc, char *argv[]) { int sockfd, portno, n; struct sockaddr_in serv_addr; struct hostent *server; pthread_t read_message; char buffer[256]; if (argc < 3) { fprintf(stderr,"usage %s hostname port\n", argv[0]); exit(0); } portno = atoi(argv[2]); sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR opening socket"); server = gethostbyname(argv[1]); if (server == NULL) { fprintf(stderr,"ERROR, no such host\n"); exit(0); } bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length); serv_addr.sin_port = htons(portno); if (connect(sockfd,&serv_addr,sizeof(serv_addr)) < 0) error("ERROR connecting"); bzero(buffer,256); if (pthread_create(&read_message,NULL,(void *)listen_for_message,(void *)sockfd) !=0 ) { perror("error creating thread"); } while (1) { fgets(buffer,255,stdin); n = write(sockfd,buffer,256); if (n < 0) error("ERROR writing to socket"); bzero(buffer,256); } return 0; }

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  • scrolling lags in emacs 23.2 with GTK

    - by mefiX
    Hey there, I am using emacs 23.2 with the GTK toolkit. I built emacs from source using the following configure-params: ./configure --prefix=/usr --without-makeinfo --without-sound Which builds emacs with the following configuration: Where should the build process find the source code? /home/****/incoming/emacs-23.2 What operating system and machine description files should Emacs use? `s/gnu-linux.h' and `m/intel386.h' What compiler should emacs be built with? gcc -g -O2 -Wdeclaration-after-statement -Wno-pointer-sign Should Emacs use the GNU version of malloc? yes (Using Doug Lea's new malloc from the GNU C Library.) Should Emacs use a relocating allocator for buffers? yes Should Emacs use mmap(2) for buffer allocation? no What window system should Emacs use? x11 What toolkit should Emacs use? GTK Where do we find X Windows header files? Standard dirs Where do we find X Windows libraries? Standard dirs Does Emacs use -lXaw3d? no Does Emacs use -lXpm? yes Does Emacs use -ljpeg? yes Does Emacs use -ltiff? yes Does Emacs use a gif library? yes -lgif Does Emacs use -lpng? yes Does Emacs use -lrsvg-2? no Does Emacs use -lgpm? yes Does Emacs use -ldbus? yes Does Emacs use -lgconf? no Does Emacs use -lfreetype? yes Does Emacs use -lm17n-flt? no Does Emacs use -lotf? yes Does Emacs use -lxft? yes Does Emacs use toolkit scroll bars? yes When I'm scrolling within files of a common size (about 1000 lines) holding the up/down-keys, emacs almost hangs and produces about 50% CPU-load. I use the following plugins: ido linum tabbar auto-complete-config Starting emacs with -q fixes the problem, but then I don't have any plugins. I can't figure out, which part of my .emacs is responsible for this behaviour. Here's an excerpt of my .emacs-file: (require 'ido) (ido-mode 1) (require 'linum) (global-linum-mode 1) (require 'tabbar) (tabbar-mode 1) (tabbar-local-mode 0) (tabbar-mwheel-mode 0) (setq tabbar-buffer-groups-function (lambda () (list "All"))) (global-set-key [M-left] 'tabbar-backward) (global-set-key [M-right] 'tabbar-forward) ;; hide the toolbar (gtk etc.) (tool-bar-mode -1) ;; Mouse scrolling enhancements (setq mouse-wheel-progressive-speed nil) (setq mouse-wheel-scroll-amount '(5 ((shift) . 5) ((control) . nil))) ;; Smart-HOME (defun smart-beginning-of-line () "Forces the cursor to jump to the first none whitespace char of the current line when pressing HOME" (interactive) (let ((oldpos (point))) (back-to-indentation) (and (= oldpos (point)) (beginning-of-line)))) (put 'smart-beginning-of-line 'CUA 'move) (global-set-key [home] 'smart-beginning-of-line) (custom-set-variables ;; custom-set-variables was added by Custom. ;; If you edit it by hand, you could mess it up, so be careful. ;; Your init file should contain only one such instance. ;; If there is more than one, they won't work right. '(column-number-mode t) '(cua-mode t nil (cua-base)) '(custom-buffer-indent 4) '(delete-selection-mode nil) '(display-time-24hr-format t) '(display-time-day-and-date 1) '(display-time-mode t) '(global-font-lock-mode t nil (font-lock)) '(inhibit-startup-buffer-menu t) '(inhibit-startup-screen t) '(pc-select-meta-moves-sexps t) '(pc-select-selection-keys-only t) '(pc-selection-mode t nil (pc-select)) '(scroll-bar-mode (quote right)) '(show-paren-mode t) '(standard-indent 4) '(uniquify-buffer-name-style (quote forward) nil (uniquify))) (setq-default tab-width 4) (setq-default indent-tabs-mode t) (setq c-basic-offset 4) ;; Highlighting of the current line (global-hl-line-mode 1) (set-face-background 'hl-line "#E8F2FE") (defalias 'yes-or-no-p 'y-or-n-p) (display-time) (set-language-environment "Latin-1") ;; Change cursor color according to mode (setq djcb-read-only-color "gray") ;; valid values are t, nil, box, hollow, bar, (bar . WIDTH), hbar, ;; (hbar. HEIGHT); see the docs for set-cursor-type (setq djcb-read-only-cursor-type 'hbar) (setq djcb-overwrite-color "red") (setq djcb-overwrite-cursor-type 'box) (setq djcb-normal-color "black") (setq djcb-normal-cursor-type 'bar) (defun djcb-set-cursor-according-to-mode () "change cursor color and type according to some minor modes." (cond (buffer-read-only (set-cursor-color djcb-read-only-color) (setq cursor-type djcb-read-only-cursor-type)) (overwrite-mode (set-cursor-color djcb-overwrite-color) (setq cursor-type djcb-overwrite-cursor-type)) (t (set-cursor-color djcb-normal-color) (setq cursor-type djcb-normal-cursor-type)))) (add-hook 'post-command-hook 'djcb-set-cursor-according-to-mode) (define-key global-map '[C-right] 'forward-sexp) (define-key global-map '[C-left] 'backward-sexp) (define-key global-map '[s-left] 'windmove-left) (define-key global-map '[s-right] 'windmove-right) (define-key global-map '[s-up] 'windmove-up) (define-key global-map '[s-down] 'windmove-down) (define-key global-map '[S-down-mouse-1] 'mouse-stay-and-copy) (define-key global-map '[C-M-S-down-mouse-1] 'mouse-stay-and-swap) (define-key global-map '[S-mouse-2] 'mouse-yank-and-kill) (define-key global-map '[C-S-down-mouse-1] 'mouse-stay-and-kill) (define-key global-map "\C-a" 'mark-whole-buffer) (custom-set-faces ;; custom-set-faces was added by Custom. ;; If you edit it by hand, you could mess it up, so be careful. ;; Your init file should contain only one such instance. ;; If there is more than one, they won't work right. '(default ((t (:inherit nil :stipple nil :background "#f7f9fa" :foreground "#191919" :inverse-video nil :box nil :strike-through nil :overline nil :underline nil :slant normal :weight normal :height 98 :width normal :foundry "unknown" :family "DejaVu Sans Mono")))) '(font-lock-builtin-face ((((class color) (min-colors 88) (background light)) (:foreground "#642880" :weight bold)))) '(font-lock-comment-face ((((class color) (min-colors 88) (background light)) (:foreground "#3f7f5f")))) '(font-lock-constant-face ((((class color) (min-colors 88) (background light)) (:weight bold)))) '(font-lock-doc-face ((t (:inherit font-lock-string-face :foreground "#3f7f5f")))) '(font-lock-function-name-face ((((class color) (min-colors 88) (background light)) (:foreground "Black" :weight bold)))) '(font-lock-keyword-face ((((class color) (min-colors 88) (background light)) (:foreground "#7f0055" :weight bold)))) '(font-lock-preprocessor-face ((t (:inherit font-lock-builtin-face :foreground "#7f0055" :weight bold)))) '(font-lock-string-face ((((class color) (min-colors 88) (background light)) (:foreground "#0000c0")))) '(font-lock-type-face ((((class color) (min-colors 88) (background light)) (:foreground "#7f0055" :weight bold)))) '(font-lock-variable-name-face ((((class color) (min-colors 88) (background light)) (:foreground "Black")))) '(minibuffer-prompt ((t (:foreground "medium blue")))) '(mode-line ((t (:background "#222222" :foreground "White")))) '(tabbar-button ((t (:inherit tabbar-default :foreground "dark red")))) '(tabbar-button-highlight ((t (:inherit tabbar-default :background "white" :box (:line-width 2 :color "white"))))) '(tabbar-default ((t (:background "gray90" :foreground "gray50" :box (:line-width 3 :color "gray90") :height 100)))) '(tabbar-highlight ((t (:underline t)))) '(tabbar-selected ((t (:inherit tabbar-default :foreground "blue" :weight bold)))) '(tabbar-separator ((t nil))) '(tabbar-unselected ((t (:inherit tabbar-default))))) Any suggestions? Kind regards, mefiX

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