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• The woes of (sometimes) storing "date only" in datetimes

  - by Heinzi

  We have two fields from and to (of type datetime), where the user can store the begin time and the end time of a business trip, e.g.: From: 2010-04-14 09:00 To: 2010-04-16 16:30 So, the duration of the trip is 2 days and 7.5 hours. Often, the exact times are not known in advance, so the user enters the dates without a time: From: 2010-04-14 To: 2010-04-16 Internally, this is stored as 2010-04-14 00:00 and 2010-04-16 00:00, since that's what most modern class libraries (e.g. .net) and databases (e.g. SQL Server) do when you store a "date only" in a datetime structure. Usually, this makes perfect sense. However, when entering 2010-04-16 as the to date, the user clearly did not mean 2010-04-16 00:00. Instead, the user meant 2010-04-16 24:00, i.e., calculating the duration of the trip should output 3 days, not 2 days. I can think of a few (more or less ugly) workarounds for this problem (add "23:59" in the UI layer of the to field if the user did not enter a time component; add a special "dates are full days" Boolean field; store "2010-04-17 00:00" in the DB but display "2010-04-16 24:00" to the user if the time component is "00:00"; ...), all having advantages and disadvantages. Since I assume that this is a fairly common problem, I was wondering: Is there a "standard" best-practice way of solving it? If there isn't, have you experienced a similar requirement, how did you solve it and what were the pros/cons of that solution?

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• Questions on usages of sizeof

  - by Appu

  Question 1 I have a struct like, struct foo { int a; char c; }; When I say sizeof(foo), i am getting 8 on my machine. As per my understanding, 4 bytes for int, 1 byte for char and 3 bytes for padding. Is that correct? Given a struct like the above, how will I find out how many bytes will be added as padding? Question 2 I am aware that sizeof can be used to calculate the size of an array. Mostly I have seen the usage like (foos is an array of foo) sizeof(foos)/sizeof(*foos) But I found that the following will also give same result. sizeof(foos) / sizeof(foo) Is there any difference in these two? Which one is preffered? Question 3 Consider the following statement. foo foos[] = {10,20,30}; When I do sizeof(foos) / sizeof(*foos), it gives 2. But the array has 3 elements. If I change the statement to foo foos[] = {{10},{20},{30}}; it gives correct result 3. Why is this happening? Any thoughts..

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• What is the best practice about rewinding streams?

  - by juancalero

  I've done the same mistake lots of times: I've tried to use a Stream that is positioned in the end, consequently returning nothing. When and how is the best way to rewind the Stream (setting the Position to 0) after "loading" it?

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• How would you organize a large complex web application (see basic example)?

  - by Anurag

  How do you usually organize complex web applications that are extremely rich on the client side. I have created a contrived example to indicate the kind of mess it's easy to get into if things are not managed well for big apps. Feel free to modify/extend this example as you wish - http://jsfiddle.net/NHyLC/1/ The example basically mirrors part of the comment posting on SO, and follows the following rules: Must have 15 characters minimum, after multiple spaces are trimmed out to one. If Add Comment is clicked, but the size is less than 15 after removing multiple spaces, then show a popup with the error. Indicate amount of characters remaining and summarize with color coding. Gray indicates a small comment, brown indicates a medium comment, orange a large comment, and red a comment overflow. One comment can only be submitted every 15 seconds. If comment is submitted too soon, show a popup with appropriate error message. A couple of issues I noticed with this example. This should ideally be a widget or some sort of packaged functionality. Things like a comment per 15 seconds, and minimum 15 character comment belong to some application wide policies rather than being embedded inside each widget. Too many hard-coded values. No code organization. Model, Views, Controllers are all bundled together. Not that MVC is the only approach for organizing rich client side web applications, but there is none in this example. How would you go about cleaning this up? Applying a little MVC/MVP along the way? Here's some of the relevant functions, but it will make more sense if you saw the entire code on jsfiddle: /** * Handle comment change. * Update character count. * Indicate progress */ function handleCommentUpdate(comment) { var status = $('.comment-status'); status.text(getStatusText(comment)); status.removeClass('mild spicy hot sizzling'); status.addClass(getStatusClass(comment)); } /** * Is the comment valid for submission */ function commentSubmittable(comment) { var notTooSoon = !isTooSoon(); var notEmpty = !isEmpty(comment); var hasEnoughCharacters = !isTooShort(comment); return notTooSoon && notEmpty && hasEnoughCharacters; } // submit comment $('.add-comment').click(function() { var comment = $('.comment-box').val(); // submit comment, fake ajax call if(commentSubmittable(comment)) { .. } // show a popup if comment is mostly spaces if(isTooShort(comment)) { if(comment.length < 15) { // blink status message } else { popup("Comment must be at least 15 characters in length."); } } // show a popup is comment submitted too soon else if(isTooSoon()) { popup("Only 1 comment allowed per 15 seconds."); } });

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• Is it proper to get and especially set Perl module's global variables directly?

  - by DVK

  I was wondering what the best practice in Perl is regarding getting - or, more importantly, setting - a global variable of some module by directly accessing $Module::varName in case the module didn't provide getter/setter method for it. The reason it smells bad to me is the fact that it sort of circumvents encapsulation. Just because I can do it in Perl, I'm not entirely certain I should (assuming there actually is an alternative such as adding a getter/setter to the module). I'm asking this because I'm about to request an addition of a getter/setter for a global variable in one of the core Perl modules, and I would like to avoid it soundly and unanimously rejected on the grounds of "Why the heck do you need one when you can access the variable in the package directly?" - in case doing the latter is actually considered perfectly OK by the community.

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• WordPress: Image In Every Post

  - by Sarfraz

  Hello, If you visit this site: http://www.catswhocode.com/blog/ You would see that there is an image and summary for each post. What is the proper way to implement that? Is this done using wordpress custom fields? Or whether this is coded in image.php file present in theme folder? How do i do that? Thanks

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• Amazon SimpleDB Identity Seed equivalent

  - by Zaff

  Is there an equivalent to an identity Seed in SimpleDB? If the answer is no, how do you handle creating something like a customer number or order number that will prevent the creation duplicate numbers? My experience is mainly from SQL Server in which I would either create a primary key with an identity seed or use transactions in a stored procedure to increment the number. Thanks for your help!

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• Fluent API Style Usage

  - by Chris Dwyer

  When programming against a fluent API, I've seen the style mostly like this: var obj = objectFactory.CreateObject() .SetObjectParameter(paramName, value) .SetObjectParameter(paramName, value) .DoSomeTransformation(); What is the reasoning behind putting the dot at the beginning of the line instead of the end of the line like this: var obj = objectFactory.CreateObject(). SetObjectParameter(paramName, value). SetObjectParameter(paramName, value). DoSomeTransformation(); Or, is it merely a style thing that a team makes a consensus on?

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• How To improve ASP.NET MVC Application Performance

  - by SDReyes

  How do you improve your ASP.NET MVC application performance?

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• hover effect jQuery

  - by Ori Cohen

  I have a bunch of li elements that I want to alternate in color using odds and evens, and then highlight based on mouse hover. In order to un-highlight I need to keep track of what the color used to be, odd or even. To do this when I apply the highlight color, I first set an arbitrary attribute to it. Are there any downsides to doing it this way? Is there a better way? Here's the code: <script type="text/javascript"> var init = function(event){ $("li:odd").css({'background-color' : '#eeeeee', 'font-weight' : 'bold'}); $("li:even").css('background-color', '#cccccc'); //initial colors setup $("li").hover( function () //hover over { var current = $(this); current.attr('old-background', current.css('background-color')); current.css('background-color', '#ffee99'); } , function() //hover out { var current = $(this); current.css('background-color', current.attr('old-background')); }) } $(document).ready(init); </script> So is there a better way to do this?

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• Prefer extension methods for encapsulation and reusability?

  - by tzaman

  edit4: wikified, since this seems to have morphed more into a discussion than a specific question. In C++ programming, it's generally considered good practice to "prefer non-member non-friend functions" instead of instance methods. This has been recommended by Scott Meyers in this classic Dr. Dobbs article, and repeated by Herb Sutter and Andrei Alexandrescu in C++ Coding Standards (item 44); the general argument being that if a function can do its job solely by relying on the public interface exposed by the class, it actually increases encapsulation to have it be external. While this confuses the "packaging" of the class to some extent, the benefits are generally considered worth it. Now, ever since I've started programming in C#, I've had a feeling that here is the ultimate expression of the concept that they're trying to achieve with "non-member, non-friend functions that are part of a class interface". C# adds two crucial components to the mix - the first being interfaces, and the second extension methods: Interfaces allow a class to formally specify their public contract, the methods and properties that they're exposing to the world. Any other class can choose to implement the same interface and fulfill that same contract. Extension methods can be defined on an interface, providing any functionality that can be implemented via the interface to all implementers automatically. And best of all, because of the "instance syntax" sugar and IDE support, they can be called the same way as any other instance method, eliminating the cognitive overhead! So you get the encapsulation benefits of "non-member, non-friend" functions with the convenience of members. Seems like the best of both worlds to me; the .NET library itself providing a shining example in LINQ. However, everywhere I look I see people warning against extension method overuse; even the MSDN page itself states: In general, we recommend that you implement extension methods sparingly and only when you have to. (edit: Even in the current .NET library, I can see places where it would've been useful to have extensions instead of instance methods - for example, all of the utility functions of List<T> (Sort, BinarySearch, FindIndex, etc.) would be incredibly useful if they were lifted up to IList<T> - getting free bonus functionality like that adds a lot more benefit to implementing the interface.) So what's the verdict? Are extension methods the acme of encapsulation and code reuse, or am I just deluding myself? (edit2: In response to Tomas - while C# did start out with Java's (overly, imo) OO mentality, it seems to be embracing more multi-paradigm programming with every new release; the main thrust of this question is whether using extension methods to drive a style change (towards more generic / functional C#) is useful or worthwhile..) edit3: overridable extension methods The only real problem identified so far with this approach, is that you can't specialize extension methods if you need to. I've been thinking about the issue, and I think I've come up with a solution. Suppose I have an interface MyInterface, which I want to extend - I define my extension methods in a MyExtension static class, and pair it with another interface, call it MyExtensionOverrider. MyExtension methods are defined according to this pattern: public static int MyMethod(this MyInterface obj, int arg, bool attemptCast=true) { if (attemptCast && obj is MyExtensionOverrider) { return ((MyExtensionOverrider)obj).MyMethod(arg); } // regular implementation here } The override interface mirrors all of the methods defined in MyExtension, except without the this or attemptCast parameters: public interface MyExtensionOverrider { int MyMethod(int arg); string MyOtherMethod(); } Now, any class can implement the interface and get the default extension functionality: public class MyClass : MyInterface { ... } Anyone that wants to override it with specific implementations can additionally implement the override interface: public class MySpecializedClass : MyInterface, MyExtensionOverrider { public int MyMethod(int arg) { //specialized implementation for one method } public string MyOtherMethod() { // fallback to default for others MyExtension.MyOtherMethod(this, attemptCast: false); } } And there we go: extension methods provided on an interface, with the option of complete extensibility if needed. Fully general too, the interface itself doesn't need to know about the extension / override, and multiple extension / override pairs can be implemented without interfering with each other. I can see three problems with this approach - It's a little bit fragile - the extension methods and override interface have to be kept synchronized manually. It's a little bit ugly - implementing the override interface involves boilerplate for every function you don't want to specialize. It's a little bit slow - there's an extra bool comparison and cast attempt added to the mainline of every method. Still, all those notwithstanding, I think this is the best we can get until there's language support for interface functions. Thoughts?

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• How can I write classes that don't rely on "global" variables?

  - by Joel

  When I took my first programming course in university, we were taught that global variables were evil & should be avoided at all cost (since you can quickly develop confusing and unmaintainable code). The following year, we were taught object oriented programming, and how to create modular code using classes. I find that whenever I work with OOP, I use my classes' private variables as global variables, i.e., they can be (and are) read and modified by any function within the class. This isn't really sitting right with me, as it seems to introduce the same problems global variables had in languages like C. So I guess my question is, how do I stop writing classes with "global" variables? Would it make more sense to pretend I'm writing in a functional language? By this I mean having all functions take parameters & return values instead of directly modifying class variables. If I need to set any fields, I can just take the output of the function and assign it instead of having the function do it directly. This seems like it might make more maintainable code, at least for larger classes. What's common practice? Thanks!

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• How to handle BL cache for multiple web applications?

  - by Eran Betzalel

  I recently received a project that contains multiple web applications with no MVC structure. For starters I've created a library (DLL) that will contain the main Business Logic. The problem is with Caching - If I use the current web context cache object than I might end up with duplicate caching (as the web context will be different for every application). I'm currently thinking about implementing a simple caching mechanism with a singleton pattern that will allow the different web sites (aka different application domains) to share their "caching wisdom". I'd like to know what is the best way to solve this problem.

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• GOTO still considered harmful?

  - by Kyle Cronin

  Everyone is aware of Dijkstra's Letters to the editor: go to statement considered harmful (also here .html transcript and here .pdf) and there has been a formidable push since that time to eschew the goto statement whenever possible. While it's possible to use goto to produce unmaintainable, sprawling code, it nevertheless remains in modern programming languages. Even the advanced continuation control structure in Scheme can be described as a sophisticated goto. What circumstances warrant the use of goto? When is it best to avoid? As a followup question: C provides a pair of functions, setjmp and longjmp, that provide the ability to goto not just within the current stack frame but within any of the calling frames. Should these be considered as dangerous as goto? More dangerous? Dijkstra himself regretted that title, of which he was not responsible for. At the end of EWD1308 (also here .pdf) he wrote: Finally a short story for the record. In 1968, the Communications of the ACM published a text of mine under the title "The goto statement considered harmful", which in later years would be most frequently referenced, regrettably, however, often by authors who had seen no more of it than its title, which became a cornerstone of my fame by becoming a template: we would see all sorts of articles under the title "X considered harmful" for almost any X, including one titled "Dijkstra considered harmful". But what had happened? I had submitted a paper under the title "A case against the goto statement", which, in order to speed up its publication, the editor had changed into a "letter to the Editor", and in the process he had given it a new title of his own invention! The editor was Niklaus Wirth. A well thought out classic paper about this topic, to be matched to that of Dijkstra, is Structured Programming with go to Statements (also here .pdf), by Donald E. Knuth. Reading both helps to reestablish context and a non-dogmatic understanding of the subject. In this paper, Dijkstra's opinion on this case is reported and is even more strong: Donald E. Knuth: I believe that by presenting such a view I am not in fact disagreeing sharply with Dijkstra's ideas, since he recently wrote the following: "Please don't fall into the trap of believing that I am terribly dogmatical about [the go to statement]. I have the uncomfortable feeling that others are making a religion out of it, as if the conceptual problems of programming could be solved by a single trick, by a simple form of coding discipline!"

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• Advantages of a build server?

  - by CraigS

  I am attempting to convince my colleagues to start using a build server and automated building for our Silverlight application. I have justified it on the grounds that we will catch integration errors more quickly, and will also always have a working dev copy of the system with the latest changes. But some still don't get it. What are the most significant advantages of using a Build Server for your project?

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• Creative ways to punish (or just curb) laziness in coworkers

  - by FerretallicA

  Like the subject suggests, what are some creative ways to curb laziness in co-workers? By laziness I'm talking about things like using variable names like "inttheemplrcd" instead of "intEmployerCode" or not keeping their projects synced with SVN, not just people who use the last of the sugar in the coffee room and don't refill the jar. So far the two most effective things I've done both involve the core library my company uses. Since most of our programs are in VB.net the lack of case sensitivity is abused a lot. I've got certain features of the library using Reflection to access data in the client apps, which has a negligible performance hit and introduces case sensitivity in a lot places where it is used. In instances where we have an agreed standard which is compromised by blatant laziness I take it a step further, like the DatabaseController class which will blatantly reject any DataTable passed to it which isn't named dtSomething (ie- must begin with dt and third letter must be capitalised). It's frustrating to have to resort to things like this but it has also gradually helped drill more attention to detail into their heads. Another is adding some code to the library's initialisation function to display a big and potentially embarrassing (only if seen by a client) message advising that the program is running in debug mode. We have had many instances where projects are sent to clients built in debug mode which has a lot of implications for us (especially with regard to error recovery) and doing that has made sure they always build to release before distributing. Any other creative (ie- not StyleCop etc) approaches like this?

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• automated email downloading and treading similar messages

  - by Michael

  Okay here it is : I have built an c# console app that downloads email, save attachments , and stores the subject, from, to, body to a MS SQL Database. I use aspNetPOP3 Component to do this. I have build a front end ASP.NET application to search and view the messages. Works great. Next Steps (this is where I need help ): Now I want my users (of the asp.net app) to reply to this message send the email to the originator, and tread any additional replies back and forth on from that original message(like basecamp). This would allow my end user not to have to log-in to a system, they just continue using email (our users can as well). The question is what should I use to determine if messages are related? Subject line I think is a bad approach. I believe the best method i've seen so far is way basecamp does it, but I'm not sure how that is done, here is a real example of the reply to address from a basecamp email (I've changed the host name): [email protected] Basecamp obviously are prefixing the pre-pending a tracking id to the email address, however , when I try this with my mail service, it's rejected. Is this the best approach, is there a way I can accomplish this, is there a better approach, or even a better email component tool? Thanks, Mike

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• Managing highly repetitive code and documentation in Java

  - by polygenelubricants

  Highly repetitive code is generally a bad thing, and there are design patterns that can help minimize this. However, sometimes it's simply inevitable due to the constraints of the language itself. Take the following example from java.util.Arrays: /** * Assigns the specified long value to each element of the specified * range of the specified array of longs. The range to be filled * extends from index <tt>fromIndex</tt>, inclusive, to index * <tt>toIndex</tt>, exclusive. (If <tt>fromIndex==toIndex</tt>, the * range to be filled is empty.) * * @param a the array to be filled * @param fromIndex the index of the first element (inclusive) to be * filled with the specified value * @param toIndex the index of the last element (exclusive) to be * filled with the specified value * @param val the value to be stored in all elements of the array * @throws IllegalArgumentException if <tt>fromIndex &gt; toIndex</tt> * @throws ArrayIndexOutOfBoundsException if <tt>fromIndex &lt; 0</tt> or * <tt>toIndex &gt; a.length</tt> */ public static void fill(long[] a, int fromIndex, int toIndex, long val) { rangeCheck(a.length, fromIndex, toIndex); for (int i=fromIndex; i<toIndex; i++) a[i] = val; } The above snippet appears in the source code 8 times, with very little variation in the documentation/method signature but exactly the same method body, one for each of the root array types int[], short[], char[], byte[], boolean[], double[], float[], and Object[]. I believe that unless one resorts to reflection (which is an entirely different subject in itself), this repetition is inevitable. I understand that as a utility class, such high concentration of repetitive Java code is highly atypical, but even with the best practice, repetition does happen! Refactoring doesn't always work because it's not always possible (the obvious case is when the repetition is in the documentation). Obviously maintaining this source code is a nightmare. A slight typo in the documentation, or a minor bug in the implementation, is multiplied by however many repetitions was made. In fact, the best example happens to involve this exact class: Google Research Blog - Extra, Extra - Read All About It: Nearly All Binary Searches and Mergesorts are Broken (by Joshua Bloch, Software Engineer) The bug is a surprisingly subtle one, occurring in what many thought to be just a simple and straightforward algorithm. // int mid =(low + high) / 2; // the bug int mid = (low + high) >>> 1; // the fix The above line appears 11 times in the source code! So my questions are: How are these kinds of repetitive Java code/documentation handled in practice? How are they developed, maintained, and tested? Do you start with "the original", and make it as mature as possible, and then copy and paste as necessary and hope you didn't make a mistake? And if you did make a mistake in the original, then just fix it everywhere, unless you're comfortable with deleting the copies and repeating the whole replication process? And you apply this same process for the testing code as well? Would Java benefit from some sort of limited-use source code preprocessing for this kind of thing? Perhaps Sun has their own preprocessor to help write, maintain, document and test these kind of repetitive library code? A comment requested another example, so I pulled this one from Google Collections: com.google.common.base.Predicates lines 276-310 (AndPredicate) vs lines 312-346 (OrPredicate). The source for these two classes are identical, except for: AndPredicate vs OrPredicate (each appears 5 times in its class) "And(" vs Or(" (in the respective toString() methods) #and vs #or (in the @see Javadoc comments) true vs false (in apply; ! can be rewritten out of the expression) -1 /* all bits on */ vs 0 /* all bits off */ in hashCode() &= vs |= in hashCode()

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• Correctly use dependency injection

  - by Rune

  Me and two other colleagues are trying to understand how to best design a program. For example, I have an interface ISoda and multiple classes that implement that interface like Coke, Pepsi, DrPepper, etc.... My colleague is saying that it's best to put these items into a database like a key/value pair. For example: Key | Name -------------------------------------- Coke | my.namespace.Coke, MyAssembly Pepsi | my.namespace.Pepsi, MyAssembly DrPepper | my.namespace.DrPepper, MyAssembly ... then have XML configuration files that map the input to the correct key, query the database for the key, then create the object. I don't have any specific reasons, but I just feel that this is a bad design, but I don't know what to say or how to correctly argue against it. My second colleague is suggesting that we micro-manage each of these classes. So basically the input would go through a switch statement, something similiar to this: ISoda soda; switch (input) { case "Coke": soda = new Coke(); break; case "Pepsi": soda = new Pepsi(); break; case "DrPepper": soda = new DrPepper(); break; } This seems a little better to me, but I still think there is a better way to do it. I've been reading up on IoC containers the last few days and it seems like a good solution. However, I'm still very new to dependency injection and IoC containers, so I don't know how to correctly argue for it. Or maybe I'm the wrong one and there's a better way to do it? If so, can someone suggest a better method? What kind of arguments can I bring to the table to convince my colleagues to try another method? What are the pros/cons? Why should we do it one way? Unfortunately, my colleagues are very resistant to change so I'm trying to figure out how I can convince them.

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• Can a script called by XHR reference $_COOKIE?

  - by Christian Mann

  Quick yes/no - I'm building an AJAX application and some scripts require authentication. Can I read $_COOKIE['username'] and $_COOKIE['password'] on the server if the PHP script was called via XHR, whether that be $.get() or $.post()? Side question: Can it also set cookies? Is that considered "good practice"?

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• How to: mirror a staging server from a production server

  - by Zombies

  We want to mirror our current production app server (Oracle Application Server) onto our staging server. As it stands right now, various things are out of sync, and what may work in testing/QA can easily fail in production because of settings/patch/etc inconsistencies. I was thinking what would be best is to clone the entire disk daily and push it onto the staging server... Would this be the best method...?

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• C# integer primary key generation using Entity Framework with local database file (Sdf)

  - by Ronny

  Hello, I'm writing a standalone application and I thought using Entity Framework to store my data. At the moment the application is small so I can use a local database file to get started. The thing is that the local database file doesn't have the ability to auto generate integer primary keys as SQL Server does. Any suggestions how to manage primary keys for entities in a local database file that will be compatible with SQL Server in the future? Thanks, Ronny

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• ORM market analysis

  - by bonefisher

  I would like to see your experience with popular ORM tools outhere, like NHibernate, LLBLGen, EF, S2Q, Genom-e, LightSpeed, DataObjects.NET, OpenAccess, ... From my exp: - Genom-e is quiet capable of Linq & performance, dev support - EF lacks on some key features like lazy loading, Poco support, pers.ignorance... but in 4.o it may have overcome .. - DataObjects.Net so far good, althrough I found some bugs - NHibernate steep learning curve, no 100% Linq support (like in Genom-e and DataObjects.Net), but very supportive, extensible and mature

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• Centering a percent-based div

  - by Sarfraz

  Hello, Recently, a client asked that his site be percent-based rather than pixel-based. The percent was to be set to 80%. As you guys know, it is very easy to center the container if it is pixel-based but how do you center a percent-based main container? #container { width:80%; margin:0px auto; } That does not center the container :(

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• Whats the point of STL?

  - by Jonathan D

  I've been programming c++ for about a year now and when i'm looking about i see lots of references to STL. Can some one please tell me what it does? and the advantages and disadvantageous of it? thanks

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