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• What is best practice as far as using perl-isms (idiomatic expressions) in Perl?

  - by DVK

  A couple of years back I participated in writing the best practices/coding style for our (fairly large and often Perl-using) company. It was done by a committee of "senior" Perl developers. As anything done by consensus, it had parts which everyone disagreed with. Duh. The part that rubbed wrong the most was a strong recommendation to NOT use many Perlisms (loosely defined as code idioms not present in, say C++ or Java), such as "Avoid using '... unless X;' constructs". The main rationale posited for such rules as this one was that non-Perl developers would have much harder time with the Perl code base otherwise. The assumption here I guess is that Perl code jockeys are rarer breed overall - and among new hires to the company - than non-Perlers. I was wondering whether SO has any good arguments to support or reject this logic... it is mostly academic curiosity at this point as the company's Perl coding standard is ossified and will never be revised again as far as I'm aware. P.S. Just to be clear, the question is in the context I noted - the answer for an all-Perl smaller development shop is obviously a resounding "use Perl to its maximum capability".

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• Do the ‘up to date’ guarantees for values of Java's final fields extend to indirect references?

  - by mattbh

  The Java language spec defines semantics of final fields in section 17.5: The usage model for final fields is a simple one. Set the final fields for an object in that object's constructor. Do not write a reference to the object being constructed in a place where another thread can see it before the object's constructor is finished. If this is followed, then when the object is seen by another thread, that thread will always see the correctly constructed version of that object's final fields. It will also see versions of any object or array referenced by those final fields that are at least as up-to-date as the final fields are. My question is - does the 'up-to-date' guarantee extend to the contents of nested arrays, and nested objects? An example scenario: Thread A constructs a HashMap of ArrayLists, then assigns the HashMap to final field 'myFinal' in an instance of class 'MyClass' Thread B sees a (non-synchronized) reference to the MyClass instance and reads 'myFinal', and accesses and reads the contents of one of the ArrayLists In this scenario, are the members of the ArrayList as seen by Thread B guaranteed to be at least as up to date as they were when MyClass's constructor completed? I'm looking for clarification of the semantics of the Java Memory Model and language spec, rather than alternative solutions like synchronization. My dream answer would be a yes or no, with a reference to the relevant text.

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• Delegates in .NET: how are they constructed ?

  - by Saulius

  While inspecting delegates in C# and .NET in general, I noticed some interesting facts: Creating a delegate in C# creates a class derived from MulticastDelegate with a constructor: .method public hidebysig specialname rtspecialname instance void .ctor(object 'object', native int 'method') runtime managed { } Meaning that it expects the instance and a pointer to the method. Yet the syntax of constructing a delegate in C# suggests that it has a constructor new MyDelegate(int () target) where I can recognise int () as a function instance (int *target() would be a function pointer in C++). So obviously the C# compiler picks out the correct method from the method group defined by the function name and constructs the delegate. So the first question would be, where does the C# compiler (or Visual Studio, to be precise) pick this constructor signature from ? I did not notice any special attributes or something that would make a distinction. Is this some sort of compiler/visualstudio magic ? If not, is the T (args) target construction valid in C# ? I did not manage to get anything with it to compile, e.g.: int () target = MyMethod; is invalid, so is doing anything with MyMetod, e.g. calling .ToString() on it (well this does make some sense, since that is technically a method group, but I imagine it should be possible to explicitly pick out a method by casting, e.g. (int())MyFunction. So is all of this purely compiler magic ? Looking at the construction through reflector reveals yet another syntax: Func CS$1$0000 = new Func(null, (IntPtr) Foo); This is consistent with the disassembled constructor signature, yet this does not compile! One final interesting note is that the classes Delegate and MulticastDelegate have yet another sets of constructors: .method family hidebysig specialname rtspecialname instance void .ctor(class System.Type target, string 'method') cil managed Where does the transition from an instance and method pointer to a type and a string method name occur ? Can this be explained by the runtime managed keywords in the custom delegate constructor signature, i.e. does the runtime do it's job here ?

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• Compiling a DLL which includes Ogre3D gives an assertion error when used

  - by samaursa

  Hi, I have a framework that I am building and is being compiled into a static library to be used by other projects. The library works perfectly without issues. The problem is that the link time is very long for the projects that use the library so I thought I will make a DLL project of the same framework. I started with baby steps and created an MFC DLL project through visual studio. The project has the following header: /// -------------------------------------------- #ifndef OGRECORE_H #define OGRECORE_H #ifdef OGREFW_EXPORT #define OGREFW_DLL __declspec(dllexport) #else #define OGREFW_DLL __declspec(dllimport) #endif class OgreRoot; namespace OgreFW { class OGREFW_DLL OgreCore// : public OIS::KeyListener, public OIS::MouseListener { public: OgreCore(); ~OgreCore(); }; }; #endif // OGRECORE_H and this is the source #include "stdafx.h" #include "OgreCore.h" //#include "Ogre.h" //#include "OgreRoot.h" //#include "OgreRenderWindow.h" //#include "OgreLog.h" //#include "OgreLogManager.h" //#include "OgreOverlay.h" //#include "OgreViewport.h" //#include "OgreRenderWindow.h" //#include "OgreFrameListener.h" //#include "OgreWindowEventUtilities.h" //#include "OgreSceneNode.h" //#include "OgreEntity.h" //#include "OgreManualObject.h" //#include "OgreMeshManager.h" //#include "OgreConfigFile.h" //#include "OgreOverlayContainer.h" //#include "OgreOverlayManager.h" namespace OgreFW { OGREFW_DLL OgreCore::OgreCore() { } // ------------------------ OGREFW_DLL OgreCore::~OgreCore() { } } As you can see I have commented out Ogre includes. When a project uses the compiled DLL and constructs this (OgreCore) class, it works perfectly fine. As soon as uncomment one of the Ogre includes and compile the DLL again, the project that uses the DLL now gives an assertion error. The full details can be found here in the Ogre forum post. I posted the question there first but since its not really an Ogre specific question I thought I will try here as well. The link to the Ogre post is: http://www.ogre3d.org/forums/viewtopic.php?f=2&t=58403 Thank you in advance

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• Modify Django Forms

  - by Ninefingers

  Hi All, I've recently been developing on the django platform and have stumbled upon Django Forms (forms.Form/forms.ModelForm) as ways of creating <form> html. Now, this is brilliant for quick stuff but what I'm trying to do is a little bit more complicated. Consider a DateField - my current form has fields for day, month and year and constructs a python date object from that. However, a django form creates a single textbox in which the correct format (say 2010-06-15) must be entered. As another example, for large fields I need to replace <input> with <textarea>. I'd like to take advantage of Django's forms for simple validation but I need something simpler for my users. So my question is: can I intercept the rendering of one of these objects to write out the html as I like? If so, do I have to do all the writing myself or can I only do those objects I wish to re-write? Thanks in advance.

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• Zend Framework: How to start PHPUnit testing Forms?

  - by Andrew

  I am having trouble getting my filters/validators to work correctly on my form, so I want to create a Unit test to verify that the data I am submitting to my form is being filtered and validated correctly. I started by auto-generating a PHPUnit test in Zend Studio, which gives me this: <?php require_once 'PHPUnit/Framework/TestCase.php'; /** * Form_Event test case. */ class Form_EventTest extends PHPUnit_Framework_TestCase { /** * @var Form_Event */ private $Form_Event; /** * Prepares the environment before running a test. */ protected function setUp () { parent::setUp(); // TODO Auto-generated Form_EventTest::setUp() $this->Form_Event = new Form_Event(/* parameters */); } /** * Cleans up the environment after running a test. */ protected function tearDown () { // TODO Auto-generated Form_EventTest::tearDown() $this->Form_Event = null; parent::tearDown(); } /** * Constructs the test case. */ public function __construct () { // TODO Auto-generated constructor } /** * Tests Form_Event->init() */ public function testInit () { // TODO Auto-generated Form_EventTest->testInit() $this->markTestIncomplete( "init test not implemented"); $this->Form_Event->init(/* parameters */); } /** * Tests Form_Event->getFormattedMessages() */ public function testGetFormattedMessages () { // TODO Auto-generated Form_EventTest->testGetFormattedMessages() $this->markTestIncomplete( "getFormattedMessages test not implemented"); $this->Form_Event->getFormattedMessages(/* parameters */); } } so then I open up terminal, navigate to the directory, and try to run the test: $ cd my_app/tests/unit/application/forms $ phpunit EventTest.php Fatal error: Class 'Form_Event' not found in .../tests/unit/application/forms/EventTest.php on line 19 So then I add a require_once at the top to include my Form class and try it again. Now it says it can't find another class. I include that one and try it again. Then it says it can't find another class, and another class, and so on. I have all of these dependencies on all these other Zend_Form classes. What should I do? How should I go about testing my Form to make sure my Validators and Filters are being attached correctly, and that it's doing what I expect it to do. Or am I thinking about this the wrong way?

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• API Wrapper Architecture Best Practice

  - by Adam Taylor

  Hi, So I'm writing a Perl wrapper module around a REST webservice and I'm hoping to have some advice on how best to architect the module. I've been looking at a couple of different Perl modules for inspiration. Flickr::Simple2 - so this is basically one big file with methods wrapping around the different methods in the Flickr API, e.g. getPhotos() etc. Flickr::API - this is a sub-class of another module (LWP) for making HTTP requests. So basically it just allows you to make calls through the module, using LWP, that go to the correct API method/URL without defining any wrapper methods itself. (That's explained pretty poorly - but basically it has a method that takes an argument (a API method name) and constructs the correct API call). e.g request() / response(). An alternative design would be like the first described, but less monolithic, with separate classes for separate "areas" of the API. I'd like to follow modern/best practice Perl methods so I'm using Dist::Zilla to build the module and Moose for the OO stuff but I'd appreciate some input on how to actually design/architect my wrapper. Guides/tutorials or pointers to other well designed modules would be appreciated. Cheers

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• Generating all unique combinations for "drive ya nuts" puzzle

  - by Yuval A

  A while back I wrote a simple python program to brute-force the single solution for the drive ya nuts puzzle. The puzzle consists of 7 hexagons with the numbers 1-6 on them, and all pieces must be aligned so that each number is adjacent to the same number on the next piece. The puzzle has ~1.4G non-unique possibilities: you have 7! options to sort the pieces by order (for example, center=0, top=1, continuing in clockwise order...). After you sorted the pieces, you can rotate each piece in 6 ways (each piece is a hexagon), so you get 6**7 possible rotations for a given permutation of the 7 pieces. Totalling: 7!*(6**7)=~1.4G possibilities. The following python code generates these possible solutions: def rotations(p): for i in range(len(p)): yield p[i:] + p[:i] def permutations(l): if len(l)<=1: yield l else: for perm in permutations(l[1:]): for i in range(len(perm)+1): yield perm[:i] + l[0:1] + perm[i:] def constructs(l): for p in permutations(l): for c in product(*(rotations(x) for x in p)): yield c However, note that the puzzle has only ~0.2G unique possible solutions, as you must divide the total number of possibilities by 6 since each possible solution is equivalent to 5 other solutions (simply rotate the entire puzzle by 1/6 a turn). Is there a better way to generate only the unique possibilities for this puzzle?

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• Using Groovy as a scripting language...

  - by Zombies

  I prefer to use scripting languages for short tasks, anything such as a really simple http bot, bulk importing/exporting data to/from somewhere, etc etc... Basic throw-away scripts and simple stuff. The point being, that a scripting language is just an efficient tool to write quick programs with. As for my understanding of Groovy at this point... If you were to program in Groovy, and you wan't to write a quick script, wouldn't you be forced to going back to regular java syntax (and we know how that can be convoluted compared to a scripting language) in order to do anything more complicated? For example, if I want to do some http scripting, wouldn't I just be right back at using java syntax to invoke Commons HttpClient? To me, the point of a scripting language is for quickly typed and less forced constructs. And here is another thing, it doesn't seem that there is any incentive for groovy based libraries to be developed when there are already so many good java one's out there, thus making groovy appear to be a Java dependent language with minor scripting features. So right now I am wondering if I could switch to Groovy as a scripting language or continue to use a more common scripting language such as Perl, Python or Ruby.

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• What AOP tools exist for doing aspect-oriented programming at the assembly language level against x8

  - by JohnnySoftware

  Looking for a tool I can use to do aspect-oriented programming at the assembly language level. For experimentation purposes, I would like the code weaver to operate native application level executable and dynamic link libraries. I have already done object-oriented AOP. I know assembly language for x86 and so forth. I would like to be able to do logging and other sorts of things using the familiar before/after/around constructs. I would like to be able to specify certain instructions or sequences/patterns of consecutive instructions as what to do a pointcut on since assembly/machine language is not exactly the most semantically rich computer language on the planet. If debugger and linker symbols are available, naturally, I would like to be able to use them to identify subroutines' entry points , branch/call/jump target addresses, symbolic data addresses, etc. I would like the ability to send notifications out to other diagnostic tools. Thus, support for sending data through connection-oriented sockets and datagrams is highly desirable. So is normal logging to files, UI, etc. This can be done using the action part of an aspect to make a function call, but then there are portability issues so the tool needs to support a flexible, well-abstracted logging/notifying mechanism with a clean, simple yet flexible. The goal is rapid-QA. The idea is to be able to share aspect source code braodly within communties as well as publicly. So, there needs to be a declarative security policy file that users can share. This insures that nothing untoward that is hidden directly or indirectly in an aspect source file slips by the execution manager. The policy file format needs to be simple to read, write, modify, understand, type-in, edit, and generate. Sort of like Java .policy files. Think the exact opposite of anything resembling XML Schema files and you get the idea. Is there such a tool in existence already?

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• ASP.NET MVC Using Castle Windsor IoC

  - by Mad Halfling

  I have an app, modelled on the one from Apress Pro ASP.NET MVC that uses castle windsor's IoC to instantiate the controllers with their respective repositories, and this is working fine e.g. public class ItemController : Controller { private IItemsRepository itemsRepository; public ItemController(IItemsRepository windsorItemsRepository) { this.itemsRepository = windsorItemsRepository; } with using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using Castle.Windsor; using Castle.Windsor.Configuration.Interpreters; using Castle.Core.Resource; using System.Reflection; using Castle.Core; namespace WebUI { public class WindsorControllerFactory : DefaultControllerFactory { WindsorContainer container; // The constructor: // 1. Sets up a new IoC container // 2. Registers all components specified in web.config // 3. Registers all controller types as components public WindsorControllerFactory() { // Instantiate a container, taking configuration from web.config container = new WindsorContainer(new XmlInterpreter(new ConfigResource("castle"))); // Also register all the controller types as transient var controllerTypes = from t in Assembly.GetExecutingAssembly().GetTypes() where typeof(IController).IsAssignableFrom(t) select t; foreach (Type t in controllerTypes) container.AddComponentWithLifestyle(t.FullName, t, LifestyleType.Transient); } // Constructs the controller instance needed to service each request protected override IController GetControllerInstance(Type controllerType) { return (IController)container.Resolve(controllerType); } } } controlling the controller creation. I sometimes need to create other repository instances within controllers, to pick up data from other places, can I do this using the CW IoC, if so then how? I have been playing around with the creation of new controller classes, as they should auto-register with my existing code (if I can get this working, I can register them properly later) but when I try to instantiate them there is an obvious objection as I can't supply a repos class for the constructor (I was pretty sure that was the wrong way to go about it anyway). Any help (especially examples) would be much appreciated. Cheers MH

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• What is a good standard exercise to learn the OO features of a language?

  - by FarmBoy

  When I'm learning a new language, I often program some mathematical functions to get used to the control flow syntax. After that, I like to implement some sorting algorithms to get used to the array/list constructs. But I don't have a standard exercise for exploring the languages OO features. Does anyone have a stock exercise for this? A good answer would naturally lend to inheritance, polymorphism, etc., for a programmer already comfortable with these concepts. An ideal answer would be one that could be communicated in a few words, without ambiguity, in the way that "implement mergesort" is completely unambiguous. (As an example, answering "design a game" is so vague as to be useless.) Any ideas? EDIT: I have to remark that the results here are somewhat ironic. 10 upvotes and (originally) 5 favorites suggest that this is a question others are interested in. Yet the most upvoted answer is one that says there is no good answer. Oh well. I think I'll look at the textbook below, I've found games useful in the past for OO.

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• Alternative Control Structures

  - by Brock Woolf

  I've been wondering about alternative ways to write control structures. One that you learn early on for if statements is a replacement for this: if ( x ) { // true } else { // false } with this (sometimes this is more readable compared to lots of brackets): x ? true : false It got me thinking. Can we replace anything else incase it's more readable. We of course replace if statements like this: if (a < b) { return true; } else { return false; } with things like this: return a < b; We can save a long if with something like this (pretty much same as the one above): bool xCollisionTrue = (object.xPos < aabb.maxX && object.xPos > aabb.minX); So those are the ones I can think of off the top of my head for the if statement and doing comparisons. So I'm wondering what about looping constructs, for, while, etc. Maybe the code obfuscators might have some ideas.

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• How to get around the jslint error 'Don't make functions within a loop.'

  - by Ernelli

  I am working on making all of our JS code pass through jslint, sometimes with a lot of tweaking with the options to get legacy code pass for now on with the intention to fix it properly later. There is one thing that jslint complains about that I do not have a workround for. That is when using constructs like this, we get the error 'Don't make functions within a loop.' for (prop in newObject) { // Check if we're overwriting an existing function if (typeof newObject[prop] === "function" && typeof _super[prop] === "function" && fnTest.test(newObject[prop])) { prototype[prop] = (function (name, func) { return function () { var result, old_super; old_super = this._super; this._super = _super[name]; result = func.apply(this, arguments); this._super = old_super; return result; }; })(prop, newObject[prop]); } This loop is part of a JS implementation of classical inheritance where classes that extend existing classes retain the super property of the extended class when invoking a member of the extended class. Just to clarify, the implementation above is inspired by this blog post by John Resig. But we also have other instances of functions created within a loop. The only workaround so far is to exclude these JS files from jslint, but we would like to use jslint for code validation and syntax checking as part of our continuous integration and build workflow. Is there a better way to implement functionality like this or is there a way to tweak code like this through jslint?

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• How to construct LambdaExpression with conversion

  - by nerijus

  I need to sort in ajax response grid by column name. Column value is number stored as a string. Let's say some trivial class (in real-life situation there is no possibility to modify this class): class TestObject { public TestObject(string v) { this.Value = v; } public string Value { get; set; } } then simple test: [Test] public void LambdaConstructionTest() { var queryable = new List<TestObject> { new TestObject("5"), new TestObject("55"), new TestObject("90"), new TestObject("9"), new TestObject("09"), new TestObject("900"), }.AsQueryable(); var sortingColumn = "Value"; ParameterExpression parameter = Expression.Parameter(queryable.ElementType); MemberExpression property = Expression.Property(parameter, sortingColumn); //// tried this one: var c = Expression.Convert(property, typeof(double)); LambdaExpression lambda = Expression.Lambda(property, parameter); //// constructs: o=>o.Value var callExpression = Expression.Call(typeof (Double), "Parse", null, property); var methodCallExpression = Expression.Call( typeof(Queryable), "OrderBy", new[] { queryable.ElementType, property.Type }, queryable.Expression, Expression.Quote(lambda)); // works, but sorts by string values. //Expression.Quote(callExpression)); // getting: System.ArgumentException {"Quoted expression must be a lambda"} var querable = queryable.Provider.CreateQuery<TestObject>(methodCallExpression); // return querable; // <- this is the return of what I need. } Sorry for not being clear in my first post as @SLaks answer was correct but I do not know how to construct correct lambda expression in this case.

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• Poor LLVM JIT performance

  - by Paul J. Lucas

  I have a legacy C++ application that constructs a tree of C++ objects. I want to use LLVM to call class constructors to create said tree. The generated LLVM code is fairly straight-forward and looks repeated sequences of: ; ... %11 = getelementptr [11 x i8*]* %Value_array1, i64 0, i64 1 %12 = call i8* @T_string_M_new_A_2Pv(i8* %heap, i8* getelementptr inbounds ([10 x i8]* @0, i64 0, i64 0)) %13 = call i8* @T_QueryLoc_M_new_A_2Pv4i(i8* %heap, i8* %12, i32 1, i32 1, i32 4, i32 5) %14 = call i8* @T_GlobalEnvironment_M_getItemFactory_A_Pv(i8* %heap) %15 = call i8* @T_xs_integer_M_new_A_Pvl(i8* %heap, i64 2) %16 = call i8* @T_ItemFactory_M_createInteger_A_3Pv(i8* %heap, i8* %14, i8* %15) %17 = call i8* @T_SingletonIterator_M_new_A_4Pv(i8* %heap, i8* %2, i8* %13, i8* %16) store i8* %17, i8** %11, align 8 ; ... Where each T_ function is a C "thunk" that calls some C++ constructor, e.g.: void* T_string_M_new_A_2Pv( void *v_value ) { string *const value = static_cast<string*>( v_value ); return new string( value ); } The thunks are necessary, of course, because LLVM knows nothing about C++. The T_ functions are added to the ExecutionEngine in use via ExecutionEngine::addGlobalMapping(). When this code is JIT'd, the performance of the JIT'ing itself is very poor. I've generated a call-graph using kcachegrind. I don't understand all the numbers (and this PDF seems not to include commas where it should), but if you look at the left fork, the bottom two ovals, Schedule... is called 16K times and setHeightToAtLeas... is called 37K times. On the right fork, RAGreed... is called 35K times. Those are far too many calls to anything for what's mostly a simple sequence of call LLVM instructions. Something seems horribly wrong. Any ideas on how to improve the performance of the JIT'ing?

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• Multhreading in Java

  - by Vijay Selvaraj

  I'm working with core java and IBM Websphere MQ 6.0. We have a standalone module say DBcomponent that hits the database and fetches a resultset based on the runtime query. The query is passed to the application via MQ messaging medium. We have a trigger configured for the queue which invokes the DBComponent whenever a message is available in the queue. The DBComponent consumes the message, constructs the query and returns the resultset to another queue. In this overall process we use log4j to log statements on a log file for auditing. The connection is pooled to the database using Apache pool. I am trying to check whether the log messages are logged correctly using a sample program. The program places the input message to the queue and checks for the logs in the log file. Its expected for the trigger method invocation to complete before i try to check for the message in log file, but every time my program to check for log message gets executed first leading my check to failure. Even if i introduce a Thread.sleep(time) doesn't solves the case. How can i make it to keep my method execution waiting until the trigger operation completes? Any suggestion will be helpful.

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• How do I use a modalViewController Identically in Two Controllers?

  - by Theory

  I'm using the Three20 TTMessageController in my app. I've figured out how to use it, adding on a bunch of other stuff (including TTMessageControllerDelegate methods and ABPeoplePickerNavigationControllerDelegate methods). It works great for me, after a bit of a struggle to figure it out. The trouble I'm having now is a design issue: I want to use it identically in two different places, including with the same delegate methods. My current approach is that I've put all the code into a single class inheriting from NSObject, called ComposerProxy, and I'm just having the two controllers that use it use the proxy, like so: ComposerProxy *proxy = [[ComposerProxy alloc] initWithController:this]; [proxy go]; The go method constructs the TTMessageController, configures it, adds it to a UINavigationController, and presents it: [self.controller presentModalViewController: navController animated: YES]; This works great, as I have all my code nicely encapsulated in ComposerProxy and I need only the above two lines anywhere I want to use it. The downside, though, is that I can't dealloc the proxy variable without getting crashes. I can't autorelease it, either: same problem. So I'm wondering if my proxy approach is a poor one. How does one normally encapsulate a bunch of behaviors like this without requiring a lot of duplicate code in the classes that use it? Do I need to add a delegate class to my ComposerProxy and make the controller responsible for dismissing the modal view controller in a hypothetical composerDidFinish method or some such? Many TIA!

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• Do fluent interfaces significantly impact runtime performance of a .NET application?

  - by stakx

  I'm currently occupying myself with implementing a fluent interface for an existing technology, which would allow code similar to the following snippet: using (var directory = Open.Directory(@"path\to\some\directory")) { using (var file = Open.File("foobar.html").In(directory)) { // ... } } In order to implement such constructs, classes are needed that accumulate arguments and pass them on to other objects. For example, to implement the Open.File(...).In(...) construct, you would need two classes: // handles 'Open.XXX': public static class OpenPhrase { // handles 'Open.File(XXX)': public static OpenFilePhrase File(string filename) { return new OpenFilePhrase(filename); } // handles 'Open.Directory(XXX)': public static DirectoryObject Directory(string path) { // ... } } // handles 'Open.File(XXX).XXX': public class OpenFilePhrase { internal OpenFilePhrase(string filename) { _filename = filename } // handles 'Open.File(XXX).In(XXX): public FileObject In(DirectoryObject directory) { // ... } private readonly string _filename; } That is, the more constituent parts statements such as the initial examples have, the more objects need to be created for passing on arguments to subsequent objects in the chain until the actual statement can finally execute. Question: I am interested in some opinions: Does a fluent interface which is implemented using the above technique significantly impact the runtime performance of an application that uses it? With runtime performance, I refer to both speed and memory usage aspects. Bear in mind that a potentially large number of temporary, argument-saving objects would have to be created for only very brief timespans, which I assume may put a certain pressure on the garbage collector. If you think there is significant performance impact, do you know of a better way to implement fluent interfaces?

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• What do I name this class whose sole purpose is to report failure?

  - by Blair Holloway

  In our system, we have a number of classes whose construction must happen asynchronously. We wrap the construction process in another class that derives from an IConstructor class: class IConstructor { public: virtual void Update() = 0; virtual Status GetStatus() = 0; virtual int GetLastError() = 0; }; There's an issue with the design of the current system - the functions that create the IConstructor-derived classes are often doing additional work which can also fail. At that point, instead of getting a constructor which can be queried for an error, a NULL pointer is returned. Restructuring the code to avoid this is possible, but time-consuming. In the meantime, I decided to create a constructor class which we create and return in case of error, instead of a NULL pointer: class FailedConstructor : public IConstructor public: virtual void Update() {} virtual Status GetStatus() { return STATUS_ERROR; } virtual int GetLastError() { return m_errorCode; } private: int m_errorCode; }; All of the above this the setup for a mundane question: what do I name the FailedConstructor class? In our current system, FailedConstructor would indicate "a class which constructs an instance of Failed", not "a class which represents a failed attempt to construct another class". I feel like it should be named for one of the design patterns, like Proxy or Adapter, but I'm not sure which.

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• Where can I find a professional image gallery built on a javascript framework?

  - by user278457

  I'm looking to find a galleria replacement, hopefully using jQuery but other javascript frameworks such as prototype or mootools are fine too. I used galleria a while back, and I need a similar product now. Unfortunately, the devkick.com domain seems to have disappeared in the meantime and I'm wary of using products that aren't actively maintained. I'm willing to pay up to $50 per site for licensing costs, if the product meets my needs. I'm specifically looking for a gallery with the following features: Every image in the gallery preloads asap, not as the user clicks "next" Minimalist default css to keep my subsequent styling headaches down, preferably a "darkroom" style by default, much as galleria looks Each element that constructs the image gallery should be simple and logical to reference with CSS As easy to install as adding a css class to a single unordered list No dependencies other than the core jQuery/other library, including "easing" and other effects must be optional Works on browsers back to IE6, Firefox 3, Safari (and iPhone), Chrome, Opera Has a javascript API that lets me trigger callback functions on common events such as "user clicks next" or "image loads" degrades gracefully without javascript, either displays images as a list, or just displays the first image in the list bonus: The gallery can display other content, such as video or external sites, like the modal boxes at shadowbox-js.com well documented minimal bandwidth requirement - .js file should be ~10kb minified bonus: The gallery source is hosted on a reliable CDN like google's bonus: Thumbnails for images do not appear until the main image has loaded bonus: includes ability to set parameters with JSON to change common behaviours, such as slide/fade transitions or automatic image switch every X seconds

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• How to rename goals in Maven?

  - by mjs

  In the Maven document Introduction to the Build Lifecycle, a goal of display:time is described that outputs the current time. The plugin is as follows: ... <plugin> <groupId>com.mycompany.example</groupId> <artifactId>maven-touch-plugin</artifactId> <version>1.0</version> <executions> <execution> <phase>process-test-resources</phase> <goals> <goal>timestamp</goal> </goals> </execution> </executions> </plugin> ... I have several questions relating to this plugin: How can I change the name of the goal to, for example, foo:bar? (Why does neither display nor time appear anywhere in the XML fragment? How can you tell, from looking at the fragment, what goals it defines?) How can I manually run this goal? (For similar constructs, the equivalent of mvn display:time sometimes works, but this doesn't work consistently.) How can I see if this goal exists? (i.e. list available goals; this question suggests this is impossible.)

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• Should a new language compiler target the JVM?

  - by Pindatjuh

  I'm developing a new language. My initial target was to compile to native x86 for the Windows platform, but now I am in doubt. I've seen some new languages target the JVM (most notable Scala and Clojure). Ofcourse it's not possible to port every language easily to the JVM; to do so, it may lead to small changes to the language and it's design. So that's the reason behind this doubt, and thus this question: Is targetting the JVM a good idea, when creating a compiler for a new language? Or should I stick with x86? I have experience in generating JVM bytecode. Are there any workarounds to JVM's GC? The language has deterministic implicit memory management. How to produce JIT-compatible bytecode, such that it will get the highest speedup? Is it similar to compiling for IA-32, such as the 4-1-1 muops pattern on Pentium? I can imagine some advantages (please correct me if I'm wrong): JVM bytecode is easier than x86. Like x86 communicates with Windows, JVM communicates with the Java Foundation Classes. To provide I/O, Threading, GUI, etc. Implementing "lightweight"-threads.I've seen a very clever implementation of this at http://www.malhar.net/sriram/kilim/. Most advantages of the Java Runtime (portability, etc.) The disadvantages, as I imagined, are: Less freedom? On x86 it'll be more easy to create low-level constructs, while JVM has a higher level (more abstract) processor. Most disadvantages of the Java Runtime (no native dynamic typing, etc.)

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• Compile time float packing/punning

  - by detly

  I'm writing C for the PIC32MX, compiled with Microchip's PIC32 C compiler (based on GCC 3.4). My problem is this: I have some reprogrammable numeric data that is stored either on EEPROM or in the program flash of the chip. This means that when I want to store a float, I have to do some type punning: typedef union { int intval; float floatval; } IntFloat; unsigned int float_as_int(float fval) { IntFloat intf; intf.floatval = fval; return intf.intval; } // Stores an int of data in whatever storage we're using void StoreInt(unsigned int data, unsigned int address); void StoreFPVal(float data, unsigned int address) { StoreInt(float_as_int(data), address); } I also include default values as an array of compile time constants. For (unsigned) integer values this is trivial, I just use the integer literal. For floats, though, I have to use this Python snippet to convert them to their word representation to include them in the array: import struct hex(struct.unpack("I", struct.pack("f", float_value))[0]) ...and so my array of defaults has these indecipherable values like: const unsigned int DEFAULTS[] = { 0x00000001, // Some default integer value, 1 0x3C83126F, // Some default float value, 0.005 } (These actually take the form of X macro constructs, but that doesn't make a difference here.) Commenting is nice, but is there a better way? It's be great to be able to do something like: const unsigned int DEFAULTS[] = { 0x00000001, // Some default integer value, 1 COMPILE_TIME_CONVERT(0.005), // Some default float value, 0.005 } ...but I'm completely at a loss, and I don't even know if such a thing is possible. Notes Obviously "no, it isn't possible" is an acceptable answer if true. I'm not overly concerned about portability, so implementation defined behaviour is fine, undefined behaviour is not (I have the IDB appendix sitting in front of me). As fas as I'm aware, this needs to be a compile time conversion, since DEFAULTS is in the global scope. Please correct me if I'm wrong about this.

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• Using Tcl DSL in Python

  - by Sridhar Ratnakumar

  I have a bunch of Python functions. Let's call them foo, bar and baz. They accept variable number of string arguments and does other sophisticated things (like accessing the network). I want the "user" (let's assume he is only familiar with Tcl) to write scripts in Tcl using those functions. Here's an example (taken from Macports) that user can come up with: post-configure { if {[variant_isset universal]} { set conflags "" foreach arch ${configure.universal_archs} { if {${arch} == "i386"} {append conflags "x86 "} else { if {${arch} == "ppc64"} {append conflags "ppc_64 "} else { append conflags ${arch} " " } } } set profiles [exec find ${worksrcpath} -name "*.pro"] foreach profile ${profiles} { reinplace -E "s|^(CONFIG\[ \\t].*)|\\1 ${conflags}|" ${profile} # Cures an isolated case system "cd ${worksrcpath}/designer && \ ${qt_dir}/bin/qmake -spec ${qt_dir}/mkspecs/macx-g++ -macx \ -o Makefile python.pro" } } } Here, variant_issset, reinplace are so on (other than Tcl builtins) are implemented as Python functions. if, foreach, set, etc.. are normal Tcl constructs. post-configure is a Python function that accepts, well, a Tcl code block that can later be executed (which in turns would obviously end up calling the above mentioned Python "functions"). Is this possible to do in Python? If so, how? from Tkinter import *; root= Tk(); root.tk.eval('puts [array get tcl_platform]') is the only integration I know of, which is obviously very limited (not to mention the fact that it starts up X11 server on mac).

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