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• Can I use a UINavigationController as the detail view of a UISplitViewController?

  - by B Sweigard

  I'm running into a problem with an iPad app where I would like to have UINavigationControllers in both of the views within a UISplitView. I've looked through other similar questions here, but most link to a tutorial online that doesn't completely solve the problem. Here's a 2-minute walkthrough to re-create the problem I'm having: Create a New Project in XCode, starting from the Split View-based Application template. Add the following NSLog statement as the first line within the DetailViewController's willHideViewController method: NSLog(@"toolbar: %@", toolbar); If you run the application now, the log will show that the DetailViewController's toolbar is alive and well. Now... Open MainWindow.xib and expand the SplitViewController. Drag a Navigation Controller from the library on top of the DetailViewController. Expand the new Navigation Controller and change the class of the UIViewController within to a DetailViewController. Ctrl-drag from the SplitViewController to the DetailViewController and assign it as the delegate. Save MainWindow.xib and run the app again. At this point, the detail view has a navigation bar and an empty toolbar. If you view the logs, you should find that the toolbar is null. Why is this? Am I missing some sort of connection in Interface Builder? Is the navigation bar the problem for some reason? Unlike the tutorial at http://www.cimgf.com/2010/05/24/fixing-the-uisplitviewcontroller-template/, I would like to keep both the navigation bar and the toolbar (preferably with the toolbar at the top when in portrait and not visible when in landscape), so that I still have a functional "Back" button when the iPad is in portrait orientation. Does anyone have any suggestions for fixing this problem? An example project with this sort of set-up would be ideal.

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• how to pass vector of string to foo(char const *const *const)?

  - by user347208

  Hi, This is my first post so please be nice. I searched in this forum and googled but I still can not find the answer. This problem has bothered me for more than a day, so please give me some help. Thank you. I need to pass a vector of string to a library function foo(char const *const *const). I can not pass the &Vec[0] since it's a pointer to a string. Therefore, I have an array and pass the c_str() to that array. The following is my code (aNames is the vector of string): const char* aR[aNames.size()]; std::transform(aNames.begin(), aNames.end(), aR, boost::bind(&std::string::c_str, _1)); foo(aR); However, it seems it causes some undefined behavior: If I run the above code, then the function foo throw some warnings about illegal characters ('èI' blablabla) in aR. If I print aR before function foo like this: std::copy(aR, aR+rowNames.size(), std::ostream_iterator<const char*>(std::cout, "\n")); foo(aR); Then, everything is fine. My questions are: Does the conversion causes undefined behavior? If so, why? What is the correct way to pass vector of string to foo(char const *const *const)? Thank you very much for your help!

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• Generic file container for quick read of data

  - by DreamCodeR

  Since there are some major privacy issues with alot of social networking sites I am trying to think about alternatives. One is to let the user keep all the information stored in some kind of file container. Now, I haven't found a single type of container that can hold "generic" information. Only for audio/video. What I want is a container that can be read by PHP with some kind of index file that lists up the users pictures in a image/ directory in the container, FOAF files (or some alternative XML-file describing users information and friends, etc.). My thoughts was to let the user keep all their information and data stored in a container that can be imported/exported and deleted from my server (the prototype social networking site I am trying to create), and then uploaded to another site that might use the same format (not that I think that will ever happen, but the user still keeps all their pictures, data, comments, messages, etc). The only thing I have come up with yet is to create a tar archive with the Archive_tar library which extracts and creates Tar-archives with an index-file describing which files are holding the messages (there might be several so each file won't be so large), what pictures are in the image/ folder and what are their names and what comments they have gotten etc. Maybe also the permissions for viewing each type of content. Does there exist any generic file format of a container that I can use to keep all this information in one file with a tree-like index file? Or must i try and create something like this myself?

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• JS best practice for member functions

  - by MickMalone1983

  I'm writing a little mobile games library, and I'm not sure the best practice for declaring member functions of instantiated function objects. For instance, I might create a simple object with one property, and a method to print it: function Foo(id){ this.id = id; this.print = function(){ console.log(this.id); }; }; However, a function which does not need access to 'private' members of the function does not need to be declared in the function at all. I could equally have written: function print(){ console.log(this.id); }; function Foo(id){ this.id = id; this.print = print; }; When the function is invoked through an instance of Foo, the instance becomes the context for this, so the output is the same in either case. I'm not entirely sure how memory is allocated with JS, and I can't find anything that I can understand about something this specific, but it seems to me that with the first example all members of Foo, including the print function, are duplicated each time it is instantiated - but with the second, it just gets a pointer to one, pre-declared function, which would save any more memory having to be allocated as more instances of Foo are created. Am I correct, and if I am, is there any memory/performance benefit to doing this?

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• Abstract away a compound identity value for use in business logic?

  - by John K

  While separating business logic and data access logic into two different assemblies, I want to abstract away the concept of identity so that the business logic deals with one consistent identity without having to understand its actual representation in the data source. I've been calling this a compound identity abstraction. Data sources in this project are swappable and various and the business logic shouldn't care which data source is currently in use. The identity is the toughest part because its implementation can change per kind of data source, whereas other fields like name, address, etc are consistently scalar values. What I'm searching for is a good way to abstract the concept of identity, whether it be an existing library, a software pattern or just a solid good idea of some kind is provided. The proposed compound identity value would have to be comparable and usable in the business logic and passed back to the data source to specify records, entities and/or documents to affect, so the data source must be able to parse back out the details of its own compound ids. Data Source Examples: This serves to provide an idea of what I mean by various data sources having different identity implementations. A relational data source might express a piece of content with an integer identifier plus a language specific code. For example. content_id language Other Columns expressing details of content 1 en_us 1 fr_ca The identity of the first record in the above example is: 1 + en_us However when a NoSQL data source is substituted, it might somehow represent each piece of content with a GUID string 936DA01F-9ABD-4d9d-80C7-02AF85C822A8 plus language code of a different standardization, And a third kind of data source might use just a simple scalar value. So on and so forth, you get the idea.

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• How to set the attributes of cell progamatically without using nib file ?

  - by srikanth rongali

  - (void)viewDidLoad { [super viewDidLoad]; // Uncomment the following line to display an Edit button in the navigation bar for this view controller. self.title = @"Library"; self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Close" style:UIBarButtonItemStyleBordered target:self action:@selector(close:)]; self.tableView.rowHeight = 80; } -(void)close:(id)sender { // } - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease]; UILabel *dateLabel = [[UILabel alloc]init]; dateLabel.frame = CGRectMake(85.0f, 6.0f, 200.0f, 20.0f); dateLabel.tag = tag1; [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator]; cell.contentView.frame = CGRectMake(0.0f, 0.0f, 320.0f, 80.0f); [cell.contentView addSubview:dateLabel]; [dateLabel release]; } // Set up the cell... //[(UILabel *)[cell viewWithTag:tag1] setText:@"Date"]; cell.textLabel.text = @"Date"; return cell; } But the control is not entering into the tableView: method. So I could not see any label in my table. How can I make this ? Thank You

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• Stop functions in 5 minutes if they dont end running

  - by george mano

  I want to add a feature in my project. I have 2 functions running in a for-loop because I want to find the solution of the functions in random arrays. I also have an function that makes random arrays. In each loop the array that is made by the random_array fun are the input of the 2 functions. The 2 functions print solutions in the screen , they dont return an argument. int main(){ for (i=0;i<50 i++) { arr1=ramdom_array(); func1(arr1) func2(arr1) } } I need to stop the functions running if they have not ended in 5 minutes. I have thought that I have to put in the functions something like this : void func1(array<array<int,4>,4> initial) { while (5minutes_not_passed) { //do staff if(solution==true) break; } } But I dont know what to put in the 5minutes_not_passed. the declaration of the functions are like this: void func1(array<array<int,4>,4> initial) void func2(array<array<int,4>,4> initial) I have found that I can use the thread library but I dont think meshing up with threads in a good idea. I believe something like a timer is needed. Note that the functions sometimes might end before 5 minutes.

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• Oracle clients dead wait

  - by Macroideal

  hi all friends I meet a problem yesterday. Maybe it's because it is April 1st... but it did exist. I have 3 PCs in remote area, two clients and one oracle server. My app is running separately in the two clients, connecting hourly to the oracle database. My clients worked well before April 1st, but suddenly my app in the client machines went down. Firstly, I did not change any configurations. I used libsqlora8 to connect to the server. I went into a dead loop in the library. I tried sqlplus, but it is dead there in my shell terminal, like it meets an infinite loop: no return until i pressed ctrl + c. The reason I guess is an "infinite loop" somewhere. BTW, when I used my local PC to connect the server, it worked well. Just from this phenomenon, we can see the problem lies in the client machine. I checked the configuration file both in local machine and client machines -they are identical Have you met a problem like this? I hope it's not due to April 1st.

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• What is good about php/what is php good for?

  - by Roman A. Taycher

  I have often seen php bashed around the webs as a loosely typed(loose typing as in a lot of type coercion and/or easy(and perhaps common) to cast object all over not dynamic typing) language without a great compiler/interpreter/vm, with even the standard library using a number of different naming conventions. A lot of people complain about perl but many (including a lot of the complainers) also give it a lot of credit for its regexes and general flexibility and power. Other then legacy code , giant web frameworks that can do tons(drupal,ect.), and easy cheap hosting what is good about php (,also what criticism are unfair, and how is the language evolving to overcome its problems). Why would i want to learn it? why would I want to do an independent project in it? The main thing I have heard is that its php codes simplicity is sometimes easier then the over-engineered complexity you find in certain Java frameworks and applications. I'm not just trolling, i'm genuinly curious what makes php programmers use it. try to convince me to put it on my languages to dabble in and languages to learn more in depth lists.

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• How do I cache jQuery selections?

  - by David

  I need to cache about 100 different selections for animating. The following is sample code. Is there a syntax problem in the second sample? If this isn't the way to cache selections, it's certainly the most popular on the interwebs. So, what am I missing? note: p in the $.path.bezier(p) below is a correctly declared object passed to jQuery.path.bezier (awesome animation library, by the way) This works $(document).ready(function() { animate1(); animate2(); }) function animate1() { $('#image1').animate({ path: new $.path.bezier(p) }, 3000); setTimeout("animate1()", 3000); } function animate2() { $('#image2').animate({ path: new $.path.bezier(p) }, 3000); setTimeout("animate2()", 3000); } This doesn't work var $one = $('#image1'); //problem with syntax here?? var $two = $('#image2'); $(document).ready(function() { animate1(); animate2(); }) function animate1() { $one.animate({ path: new $.path.bezier(p) }, 3000); setTimeout("animate1()", 3000); } function animate2() { $two.animate({ path: new $.path.bezier(p) }, 3000); setTimeout("animate2()", 3000); }

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• Program that edits string and prints each word individually with C

  - by Michael_19

  I keep getting the error segmentation fault (core dumped) when I run my progam. #include<stdio.h> #include<stdlib.h> int nextword(char *str); int main(void) { char str[] = "Hello! Today is a beautiful day!!\t\n"; int i = nextword(str); while(i != -1) { printf("%s\n",&(str[i])); i = nextword(NULL); } return 0; } int nextword(char *str) { // create two static variables - these stay around across calls static char *s; static int nextindex; int thisindex; // reset the static variables if (str != NULL) { s = str; thisindex = 0; // TODO: advance this index past any leading spaces while (s[thisindex]=='\n' || s[thisindex]=='\t' || s[thisindex]==' ' ) thisindex++; } else { // set the return value to be the nextindex thisindex = nextindex; } // if we aren't done with the string... if (thisindex != -1) { nextindex = thisindex; // TODO: two things // 1: place a '\0' after the current word // 2: advance nextindex to the beginning // of the next word while (s[nextindex] != ' ' && s[nextindex] != '\0') nextindex++; str[nextindex] = '\0'; nextindex++; } return thisindex; } The goal of the program is to print each word in the string str[] to the console on a new line. I am a beginning programmer and this is an assignment so I must use this type of format (no string library allowed). I just would like to know where I went wrong and how I can fix it.

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• Program using read() entering into an infinite loop

  - by Soham

  1oid ReadBinary(char *infile,HXmap* AssetMap) { int fd; size_t bytes_read, bytes_expected = 100000000*sizeof(char); char *data; if ((fd = open(infile,O_RDONLY)) < 0) err(EX_NOINPUT, "%s", infile); if ((data = malloc(bytes_expected)) == NULL) err(EX_OSERR, "data malloc"); bytes_read = read(fd, data, bytes_expected); if (bytes_read != bytes_expected) printf("Read only %d of %d bytes %d\n", \ bytes_read, bytes_expected,EX_DATAERR); /* ... operate on data ... */ printf("\n"); int i=0; int counter=0; char ch=data[0]; char message[512]; Message* newMessage; while(i!=bytes_read) { while(ch!='\n') { message[counter]=ch; i++; counter++; ch =data[i]; } message[counter]='\n'; message[counter+1]='\0'; //--------------------------------------------------- newMessage = (Message*)parser(message); MessageProcess(newMessage,AssetMap); //-------------------------------------------------- //printf("idNUM %e\n",newMessage->idNum); free(newMessage); i++; counter=0; ch =data[i]; } free(data); } Here, I have allocated 100MB of data with malloc, and passed a file big enough(not 500MB) size of 926KB about. When I pass small files, it reads and exits like a charm, but when I pass a big enough file, the program executes till some point after which it just hangs. I suspect it either entered an infinite loop, or there is memory leak. EDIT For better understanding I stripped away all unnecessary function calls, and checked what happens, when given a large file as input. I have attached the modified code void ReadBinary(char *infile,HXmap* AssetMap) { int fd; size_t bytes_read, bytes_expected = 500000000*sizeof(char); char *data; if ((fd = open(infile,O_RDONLY)) < 0) err(EX_NOINPUT, "%s", infile); if ((data = malloc(bytes_expected)) == NULL) err(EX_OSERR, "data malloc"); bytes_read = read(fd, data, bytes_expected); if (bytes_read != bytes_expected) printf("Read only %d of %d bytes %d\n", \ bytes_read, bytes_expected,EX_DATAERR); /* ... operate on data ... */ printf("\n"); int i=0; int counter=0; char ch=data[0]; char message[512]; while(i<=bytes_read) { while(ch!='\n') { message[counter]=ch; i++; counter++; ch =data[i]; } message[counter]='\n'; message[counter+1]='\0'; i++; printf("idNUM \n"); counter=0; ch =data[i]; } free(data); } What looks like is, it prints a whole lot of idNUM's and then poof segmentation fault I think this is an interesting behaviour, and to me it looks like there is some problem with memory FURTHER EDIT I changed back the i!=bytes_read it gives no segmentation fault. When I check for i<=bytes_read it blows past the limits in the innerloop.(courtesy gdb)

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• Populate array from vector

  - by Zag zag..

  Hi, I would like to populate an 2 dimensional array, from a vector. I think the best way to explain myself is to put some examples (with a array of [3,5] length). When vector is: [1, 0] [ [4, 3, 2, 1, 0], [4, 3, 2, 1, 0], [4, 3, 2, 1, 0] ] When vector is: [-1, 0] [ [0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4] ] When vector is: [-2, 0] [ [0, 0, 1, 1, 2], [0, 0, 1, 1, 2], [0, 0, 1, 1, 2] ] When vector is: [1, 1] [ [2, 2, 2, 1, 0], [1, 1, 1, 1, 0], [0, 0, 0, 0, 0] ] When vector is: [0, 1] [ [2, 2, 2, 2, 2], [1, 1, 1, 1, 1], [0, 0, 0, 0, 0] ] Have you got any ideas, a good library or a plan? Any comments are welcome. Thanks. Note: I consulted Ruby "Matrix" and "Vector" classes, but I don't see any way to use it in my way... Edit: In fact, each value is the number of cells (from the current cell to the last cell) according to the given vector. If we take the example where the vector is [-2, 0], with the value *1* (at array[2, 3]): array = [ [<0>, <0>, <1>, <1>, <2>], [<0>, <0>, <1>, <1>, <2>], [<0>, <0>, <1>, *1*, <2>] ] ... we could think such as: The vector [-2, 0] means that -2 is for cols and 0 is for rows. So if we are in array[2, 3], we can move 1 time on the left (left because 2 is negative) with 2 length (because -2.abs == 2). And we don't move on the top or bottom, because of 0 for rows.

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• How to know the order of component rendering in Flex

  - by Tam

  I have a component that has a sub-component they both use a shared variable from the model. The shared variable needs to be set by the parent component before it can be used by the child component. I did like this in the parent component: <mx:Canvas xmlns:mx="library://ns.adobe.com/flex/mx" ... creationComplete="group1_completeHandler(event)" > .... protected function group1_activateHandler(event:Event):void { model.myVariable = something; } .... <components:myCustomComponent> ... <components:myCustomComponent> ... </mx:Canvas> But for some reason when the code inside myCustomComponent tries to use myVariable for the first time I get a "null" object error. This means I guess that the child component gets rendered before the group1_activateHandler gets called and consequently myVariable gets set. What should I do to ensure that the parent container initializes the variable before the child component gets created?

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• dm_exec_query_stats returning stale data?

  - by VoiceOfUnreason

  I've been testing my app on a SQL Server 2005 database, and am trying to establish a preliminary picture of the query performance using sys.dm_exec_query_stats. Problem: there's a particular query that I'm interested in, because total_elapsed_time and last_elapsed_time are both large numbers. When I tickle my app to invoke that query (this runs successfully), then refresh my view of the stats, I find that 1) execution_count has incremented (expected) 2) last_execution_time has updated to now (expected) 3) last_elapsed_time is still a large value (not expected - I anticipated a new value) 4) total_elapsed_time is unchanged (contradiction?) If last_elapsed_time refers to the execution that happened @ last_execution_time, then the total_elapsed_time should have increased? This documentation: http://msdn.microsoft.com/en-us/library/ms189741(SQL.90).aspx tells me that last_execution_time is the last time the plan was executed, and last_elapsed_time comes from the "most recently executed plan", but doesn't tell me why those might be different. The query itself is uncomplicated (SELECT/WHERE/ORDER BY - parameters appearing in the where clause, but no clever operations), the table has maybe 25 rows in it right now. Questions: 1) What's the real relationship between execution_count, last_execution_time, and last_elapsed_time? 2) Where is the documentation of this relationship (manual, third party book, blog, bug ticket, stone tablets...) ?

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• How to increase my "advanced" knowledge of PHP further? (quickly)

  - by Kerry

  I have been working with PHP for years and gotten a very good grasp of the language, created many advanced and not-so-advanced systems that are working very well. The problem I'm running into is that I only learn when I find a need for something that I haven't learned before. This causes me to look up solutions and other code that handles the problem, and so I will learn about a new function or structure that I hadn't seen before. It is in this way that I have learned many of my better techniques (such as studying classes put out by Amazon, Google or other major companies). The main problem with this is the concept of not being able to learn something if you don't know it exists. For instance, it took me several months of programming to learn about the empty() function, and I simply would check the string length using strlen() to check for empty values. I'm now getting into building bigger and bigger systems, and I've started to read blogs like highscalability.com and been researching MySQL replication and server data for scaling. I know that structure of your code is very important to make full systems work. After reading a recent blog about reddit's structure, it made me question if there is some standard or "accepted systems" out there. I have looked into frameworks (I've used Kohana, which I regretted, but decided that PHP frameworks were not for me) and I prefer my own library of functions rather than having a framework. My current structure is a mix between WordPress, Kohana and my own knowledge. The ways I can see as being potentially beneficial are: Read blogs Read tutorials Work with someone else Read a book What would be the best way(s) to "get to the next level" the level of being a very good system developer?

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• how Two elements - IMG - DIV when hover over IMG show/hide the DIV - added with hover hide/show on i

  - by Jan Fosgerau

  Im very new to the wonder that is jquery. and i just figure out how to make my img buttons show/hide with a opacity difference (as such) <script type="text/javascript"> <![CDATA[ $(".ExcommKnap").mouseover(function () { $(this).stop().fadeTo('fast', 0.5, function(){}) }); $(".ExcommKnap").mouseout(function () { $(this).stop().fadeTo('fast', 1.0, function(){}) }); ]]> </script> which is good and all. but i also need to make the button when hovered over show text just above it that is specific to that button. i made these here elements that are looped in a for each. <div style="top:10px; width:755px;text-align:right; position:absolute; "> <div id="Page-{@id}" class="headlinebox"> <xsl:value-of select="@nodeName"/> </div> </div> <a href="{umbraco.library:NiceUrl(@id)}"> <img class="ExcommKnap" src="{$media/data[@alias='umbracoFile']}" /> </a> i need to make the individual text appear when hovered over its button. hence i have the id="page-{@id}" looped out along and need to get this place in the jquery code i presume. so when i hover over a img class="ExcommKnap" it makes the correct text visible. But i need the div id="page-{id}" to be invisible to begin with on pageload and then visible when its button is being hovered over. can anyone help ?

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• MySQLi Wrapper -- will this slow down performance?

  - by Kerry

  I found the following code on php.net. I'm trying to write a wrapper for the MySQLi library to make things incredibly simple. If this is going to slow down performance, I'll skip it and find another way, if this works, then I'll do that. I have a single query function, if someone passes in more than one variable, I assume the function has to be prepared. The function that I would use to pass in an array to mysqli_stmt_bind_param is call_user_func_array, I have a feeling that is going to slow things down. Am I right? <?php /* just explaining how to call mysqli_stmt_bind_param with a parameter array */ $sql_link = mysqli_connect('localhost', 'my_user', 'my_password', 'world'); $type = "isssi"; $param = array("5", "File Description", "File Title", "Original Name", time()); $sql = "INSERT INTO file_detail (file_id, file_description, file_title, file_original_name, file_upload_date) VALUES (?, ?, ?, ?, ?)"; $sql_stmt = mysqli_prepare ($sql_link, $sql); call_user_func_array('mysqli_stmt_bind_param', array_merge (array($sql_stmt, $type), $param); mysqli_stmt_execute($sql_stmt); ?>

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• Why would gnu ld link order causes Signal 11 (SEGV) on startup?

  - by Benoit

  We are building a large application in C++ that includes the use of many (static) libraries. We have a problem where the application crashes on startup with a Signal 11, before we even reach main. After much debugging, we have observed that if we explicitly reference an object file so its link order is early, the program crashes on startup. If the file is referenced later (or not referenced at all), the program does not crash. To be clear, there is NO code invoked directly from this object file. However, as it is C++, there might be static objects that do get constructed (it's a CORBA IDL generated file). We use the -Wl,--start-group ... --end-group arguments to multi-pass link the symbols since the libraries are interdependent. Here is a representation of what I mean. This is what the linker's object file order is: Order 1 Order 2 Order 3 foo.o foo.o foo.o ... ... ... main.o main.o main.o crasher.o libA.o libA.o libA.o LibB.o LibB.o LibB.o LibC.o LibC.o LibC.o crasher.o Results: NO CRASH NO CRASH CRASH Does any one have an idea why the linkage order has an effect on the crash? It would be nice if we could force the crasher.o to link later, but we're really after an explanation. Also, is there a way to force the linker to place crasher.o towards the end? Just to add to the fun, in actuality, crasher.o is part of a Library in the --start/--end-group.

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• What is Rails way to DRY up the controller pattern of verifying :id is for a valid object (else redirect to error page)

  - by jpwynn

  One of my controllers has close to 100 methods (eg routes) and nearly every one starts out the same code to redirect to an error page if the id param is invalid, followed by a similar check if the user that id doesn't belong in the user's account: def something @foo = Foo.find_by_guid(params[:id]) unless @foo @msg ||= { :title => 'No such page!', :desc => "There is no such page!" } render :action => "error" and return end unless @foo.owner_id == current_user.id @msg ||= { :title => 'Really?', :desc => "There is no such page." } render :action => "error" and return end What is the best way to DRY up that sort of page id and owner id validation, given the code is doing a render ... and return? What I don't want to do at this point is offload it to a blackbox roles and permissions library like CanCan... my goal is simply to have the in-app code to handle this be as clean as possible.

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• How does java.util.Collections.contains() perform faster than a linear search?

  - by The111

  I've been fooling around with a bunch of different ways of searching collections, collections of collections, etc. Doing lots of stupid little tests to verify my understanding. Here is one which boggles me (source code further below). In short, I am generating N random integers and adding them to a list. The list is NOT sorted. I then use Collections.contains() to look for a value in the list. I intentionally look for a value that I know won't be there, because I want to ensure that the entire list space is probed. I time this search. I then do another linear search manually, iterating through each element of the list and checking if it matches my target. I also time this search. On average, the second search takes 33% longer than the first one. By my logic, the first search must also be linear, because the list is unsorted. The only possibility I could think of (which I immediately discard) is that Java is making a sorted copy of my list just for the search, but (1) I did not authorize that usage of memory space and (2) I would think that would result in MUCH more significant time savings with such a large N. So if both searches are linear, they should both take the same amount of time. Somehow the Collections class has optimized this search, but I can't figure out how. So... what am I missing? import java.util.*; public class ListSearch { public static void main(String[] args) { int N = 10000000; // number of ints to add to the list int high = 100; // upper limit for random int generation List<Integer> ints; int target = -1; // target will not be found, forces search of entire list space long start; long end; ints = new ArrayList<Integer>(); start = System.currentTimeMillis(); System.out.print("Generating new list... "); for (int i = 0; i < N; i++) { ints.add(((int) (Math.random() * high)) + 1); } end = System.currentTimeMillis(); System.out.println("took " + (end-start) + "ms."); start = System.currentTimeMillis(); System.out.print("Searching list for target (method 1)... "); if (ints.contains(target)) { // nothing } end = System.currentTimeMillis(); System.out.println(" Took " + (end-start) + "ms."); System.out.println(); ints = new ArrayList<Integer>(); start = System.currentTimeMillis(); System.out.print("Generating new list... "); for (int i = 0; i < N; i++) { ints.add(((int) (Math.random() * high)) + 1); } end = System.currentTimeMillis(); System.out.println("took " + (end-start) + "ms."); start = System.currentTimeMillis(); System.out.print("Searching list for target (method 2)... "); for (Integer i : ints) { // nothing } end = System.currentTimeMillis(); System.out.println(" Took " + (end-start) + "ms."); } }

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• How to find "y" values of the already estimated monotone function of the non-monotone regression curve corresponding to the original "x" points?

  - by parenthesis

  The title sounds complicated but that is what I am looking for. Focus on the picture. ## data x <- c(1.009648,1.017896,1.021773,1.043659,1.060277,1.074578,1.075495,1.097086,1.106268,1.110550,1.117795,1.143573,1.166305,1.177850,1.188795,1.198032,1.200526,1.223329,1.235814,1.239068,1.243189,1.260003,1.262732,1.266907,1.269932,1.284472,1.307483,1.323714,1.326705,1.328625,1.372419,1.398703,1.404474,1.414360,1.415909,1.418254,1.430865,1.431476,1.437642,1.438682,1.447056,1.456152,1.457934,1.457993,1.465968,1.478041,1.478076,1.485995,1.486357,1.490379,1.490719) y <- c(0.5102649,0.0000000,0.6360097,0.0000000,0.8692671,0.0000000,1.0000000,0.0000000,0.4183691,0.8953987,0.3442624,0.0000000,0.7513169,0.0000000,0.0000000,0.0000000,0.0000000,0.1291901,0.4936121,0.7565551,1.0085108,0.0000000,0.0000000,0.1655482,0.0000000,0.1473168,0.0000000,0.0000000,0.0000000,0.1875293,0.4918018,0.0000000,0.0000000,0.8101771,0.6853480,0.0000000,0.0000000,0.0000000,0.0000000,0.4068802,1.1061434,0.0000000,0.0000000,0.0000000,0.0000000,0.0000000,0.0000000,0.0000000,0.0000000,0.0000000,0.6391678) fit1 <- c(0.5102649100,0.5153380934,0.5177234836,0.5255544980,0.5307668662,0.5068087080,0.5071001179,0.4825657520,0.4832969250,0.4836378194,0.4842147729,0.5004039310,0.4987301366,0.4978800742,0.4978042478,0.4969807064,0.5086987191,0.4989497612,0.4936121200,0.4922210302,0.4904593166,0.4775197108,0.4757040857,0.4729265271,0.4709141776,0.4612406896,0.4459316517,0.4351338346,0.4331439717,0.4318664278,0.3235179189,0.2907908968,0.1665721429,0.1474035158,0.1443999345,0.1398517097,0.1153991839,0.1142140393,0.1022584672,0.1002410843,0.0840033244,0.0663669309,0.0629119398,0.0627979240,0.0473336492,0.0239237481,0.0238556876,0.0084990298,0.0077970954,0.0000000000,-0.0006598571) fit2 <- c(-0.0006598571,0.0153328298,0.0228511733,0.0652889427,0.0975108758,0.1252414661,0.1270195143,0.1922510501,0.2965234797,0.3018551305,0.3108761043,0.3621749370,0.4184150225,0.4359301495,0.4432114081,0.4493565757,0.4510158144,0.4661865431,0.4744926045,0.4766574718,0.4796937554,0.4834718810,0.4836125426,0.4839450098,0.4841092849,0.4877317306,0.4930561638,0.4964939389,0.4970089201,0.4971376528,0.4990394601,0.5005881678,0.5023814257,0.5052125977,0.5056691690,0.5064254338,0.5115481820,0.5117259449,0.5146054557,0.5149729419,0.5184178197,0.5211542908,0.5216215426,0.5216426533,0.5239797875,0.5273573222,0.5273683002,0.5293994824,0.5295130266,0.5306236672,0.5307303109) ## picture plot(x, y) ## red regression curve points(x, fit1, col=2); lines(x, fit1, col=2) ## blue monotonic curve to the regression points(min(x) + cumsum(c(0, rev(diff(x)))), rev(fit2), col="blue"); lines(min(x) + cumsum(c(0, rev(diff(x)))), rev(fit2), col="blue") ## "x" original point matches with the regression estimated point ## but not with the estimated (fit2=estimate) monotonic curve abline(v=1.223329, lty=2, col="grey") Focus on the dashed grey line. The idea is to get y value of the monotonic blue curve corresponding to x original value. The grey line should cross three points (the original one "black", the regression estimate "red", the adjusted regression estimate "blue"). Can we do this? Methodology: The object "fit2" is the output of the function rearrangement(). It is always monotonically increasing. library(Rearrangement) fit2 <- rearrangement(x=as.data.frame(x), y=fit1)

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• What guarantees are there on the run-time complexity (Big-O) of LINQ methods?

  - by tzaman

  I've recently started using LINQ quite a bit, and I haven't really seen any mention of run-time complexity for any of the LINQ methods. Obviously, there are many factors at play here, so let's restrict the discussion to the plain IEnumerable LINQ-to-Objects provider. Further, let's assume that any Func passed in as a selector / mutator / etc. is a cheap O(1) operation. It seems obvious that all the single-pass operations (Select, Where, Count, Take/Skip, Any/All, etc.) will be O(n), since they only need to walk the sequence once; although even this is subject to laziness. Things are murkier for the more complex operations; the set-like operators (Union, Distinct, Except, etc.) work using GetHashCode by default (afaik), so it seems reasonable to assume they're using a hash-table internally, making these operations O(n) as well, in general. What about the versions that use an IEqualityComparer? OrderBy would need a sort, so most likely we're looking at O(n log n). What if it's already sorted? How about if I say OrderBy().ThenBy() and provide the same key to both? I could see GroupBy (and Join) using either sorting, or hashing. Which is it? Contains would be O(n) on a List, but O(1) on a HashSet - does LINQ check the underlying container to see if it can speed things up? And the real question - so far, I've been taking it on faith that the operations are performant. However, can I bank on that? STL containers, for example, clearly specify the complexity of every operation. Are there any similar guarantees on LINQ performance in the .NET library specification?

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• Why doesn't my processor have built-in BigInt support?

  - by ol

  As far as I understood it, BigInts are usually implemented in most programming languages as strings containing numbers, where, eg.: when adding two of them, each digit is added one after another like we know it from school, e.g.: 246 816 * * ---- 1062 Where * marks that there was an overflow. I learned it this way at school and all BigInt adding functions I've implemented work similar to the example above. So we all know that our processors can only natively manage ints from 0 to 2^32 / 2^64. That means that most scripting languages in order to be high-level and offer arithmetics with big integers, have to implement/use BigInt libraries that work with integers as strings like above. But of course this means that they'll be far slower than the processor. So what I've asked myself is: Why doesn't my processor have a built-in BigInt function? It would work like any other BigInt library, only (a lot) faster and at a lower level: Processor fetches one digit from the cache/RAM, adds it, and writes the result back again. Seems like a fine idea to me, so why isn't there something like that?

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• Creating a function within a loop (pointers?)

  - by user352151

  Im trying to create a simple loop that creates 50 buttons, adds them to screen and then when a button is pressed, it traces out that number. I can get it to work by doing stuff I consider hacky (such as using the buttons X/Y location to determine its value), but I'd rather just be able to hold a single value in the function. The code itself is: for (var a:int = 0; a < 5; a++) { for (var b:int = 0; b < 10; b++) { var n = (a * 10) + b + 1; var btt:SimpleButton = new BasicGameButton(); btt.x = 20 + b * 50; btt.y = 50 + a * 80; addChild(btt); btt.addEventListener(MouseEvent.CLICK, function f() { trace(n); } ); } } At the moment, whenever a button is pressed, it simply outputs "50". Is there a way of "freezing" the value of n when the function is created, for that function? (BasicGameButton is just a square button, created in the flash library) Many thanks.

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