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• Node.js for lua?

  - by Shahbaz

  I've been playing around with node.js (nodejs) for the past few day and it is fantastic. As far as I can tell, lua doesn't have a similar integration of libev and libio which let's one avoid almost any blocking calls and interact with the network and the filesystem in an asynchronous manner. I'm slowly porting my java implementation to nodejs, but I'm shocked that luajit is much faster than v8 JavaScript AND uses far less memory! I imagine writing my server in such an environment (very fast and responsive, very low memory usage, very expressive) will improve my project immensly. Being new to lua, I'm just not sure if such a thing exists. I'll appreciate any pointers. Thanks

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• Please suggest some alternative to Drupal

  - by abovesun

  Drupal propose completely different approach in web development (comparing with RoR like frameworks) and it is extremely good from development speed perspective. For example, it is quite easy to clone 90% of stackoverflow functionality using Drupal. But it has several big drawbacks: it is f''cking slow (100-400 requests per page) db structure very complicated, need at least 2 tables for easy content (entity) type, CCK fields very easy generate tons of new db tables anti-object oriented, rather aspect-oriented bad "view" layer implementation, no strange forward layouts and so on. After all this items I can say I like Drupal, but I would like something same, but more elegant and more object oriented. Probably something like http://drupy.net/ - drupal emulation on the top of django. P.S. I wrote this question not for new holy word flame, just write if you know alternative that uses something similar approach.

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• iPhone switch statement using enum

  - by Boris

  I have defined an enum in a header file of a class : typedef enum{ RED = 0, BLUE, Green } Colors; - (void) switchTest:(Colors)testColor; and in the implementation file I have : - (void) switchTest:(Colors)testColor{ if(testColor == RED){ NSLog(@"Red selected"); } switch(testColor){ case RED: NSLog(@"Red selected again !"); break; default: NSLog(@"default selected"); break; } } My code compiles correctly without warrnings. When calling the switchTest method with RED, the output is : "Red selected" but once the first line of the switch runs, the application quits unexpectedly and without warrnings/errors. I don't mind using if/else syntax but I would like to understand my mistake.

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• Grand Central Strategy for Opening Multiple Files

  - by user276632

  I have a working implementation using Grand Central dispatch queues that (1) opens a file and computes an OpenSSL DSA hash on "queue1", (2) writing out the hash to a new "side car" file for later verification on "queue2". I would like to open multiple files at the same time, but based on some logic that doesn't "choke" the OS by having 100s of files open and exceeding the hard drive's sustainable output. Photo browsing applications such as iPhoto or Aperture seem to open multiple files and display them, so I'm assuming this can be done. I'm assuming the biggest limitation will be disk I/O, as the application can (in theory) read and write multiple files simultaneously. Any suggestions? TIA

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• Why do software engineers hate writing documentation?

  - by Stewart Johnson

  I ask because I quite enjoy it! I'm talking about design documentation and implementation notes (NOT user manuals), which are non-existent in most of the codebases I've been handed. I can understand why a developer wouldn't want to write requirements (that's the analyst's job) or the user documentation (that's a technical writer's job) but I don't get why developers hate writing design docs. I don't think I would feel as if I'd finished the job if I only wrote the code and walked away -- mainly because when I've been introduced to code-only situations I've seen how hard it is to figure out what's been done and what the software does. I would hate for people to suffer the same situation when inheriting my code. What makes you loath writing supporting documentation for your code?

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• MVVM (ICommand) in Silverlight

  - by Andrey Khataev

  Hello! Please, don't judge strictly if this question was discussed previously or indirectly answered in huge nearby prism and mvvm blogs. In WPF implementation of RelayCommand or DelegateCommand classes there is a such eventhandler /// <summary> /// Occurs whenever the state of the application changes such that the result of a call to <see cref="CanExecute"/> may return a different value. /// </summary> public event EventHandler CanExecuteChanged { add { CommandManager.RequerySuggested += value; } remove { CommandManager.RequerySuggested -= value; } } but in SL subset of namespaces there are no CommandManager class. And this is where I'm stuck. I haven't yet found an workaround for this in MVVM adoptation for SL (PRISM is so complex for me yet). Different simple HelloWorldMVVM apps don't deal with at all. Thanks in advance and sorry for my English -)

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• Pure Java open-source libraries for portfolio selection (= constrained, non-linear optimization)?

  - by __roland__

  Does anyone know or has experience with a pure Java library to select portfolios or do some similar kinds of quadratic programming with constraints? There seems to be a lot of tools, as already discussed elsewhere - but what I would like to use is a pure Java implementation. Since I want to call the library from within another open-source software with a BSD-ish license I would prefer LGPL over GPL. Any help is appreciated. If you don't know such libraries, which is the most simple algorithm you would suggest to implement? It has to cope with an inequality constraint (all x_i = 0) and an equality constraint (sum of all x_i = 1).

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• Objective-C: Protocols

  - by Stu

  I'd like an instance variable object to adopt a protocol. @interface GameScene : Scene <AVAudioPlayerDelegate> { @private Layer *content <CocosNodeOpacity>; } For example I'd like my Layer object to adopt the <CocosNodeOpacity> so that I can get the methods -(GLubyte) opacity; //and -(void) setOpacity: (GLubyte) opacity; for free. The syntax shown above is invalid. Is it possible to achieve this without creating a new implementation file and creating a custom object? Thanks.

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• Grails GORM on multiple Forms

  - by Fabien Barbier

  Usually I'm using One-to-many relationship by this way : class Subject { static hasMany = [ crfs : Crf ] String name ... } class Crf { String title String info ... } I can extend this relationship to others domains, Ex : static hasMany = [ crfs : Crf, crfb : CrfBlood ...] But in my case I have to link the Subject domain to 30 others domains, maybe more...(ex : CrfBlood, CrfMedical, crfFamily, etc...). What domain model implementation should I use in my case ? I would like to keep the dynamic finders usability in my project.

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• Mathematica Plot3D does not produce a plot when graphing a user-defined function?

  - by pythonscript

  I'm writing a simple Mathematica implementation of the black-scholes model and using Plot3D to plot the pricing surface. However, when I run this code, no plot is produced. My call and put functions to produce correct values when run separately, but no plot is produced. Code: Clear[d1, d2, call, put, stockPrice, strikePrice, riskFreeRate, timeToExp, volatility] d1[stockPrice_, strikePrice_, riskFreeRate_, timeToExp_, volatility_] := (Log[stockPrice / strikePrice] + (riskFreeRate + 0.5*volatility^2)*timeToExp) / (volatility * Sqrt[timeToExp]) d2[stockPrice_, strikePrice_, riskFreeRate_, timeToExp_, volatility_] := d1[stockPrice, strikePrice, riskFreeRate, timeToExp, volatility] - volatility*Sqrt[timeToExp] call[stockPrice_, strikePrice_, riskFreeRate_, timeToExp_, volatility_] := stockPrice * CDF[NormalDistribution[0, 1], d1[stockPrice, strikePrice, riskFreeRate, timeToExp, volatility]] - strikePrice * Exp[-riskFreeRate*timeToExp] *CDF[NormalDistribution[0, 1], d2[stockPrice, strikePrice, riskFreeRate, timeToExp, volatility]] Plot3D[call[stockPrice, 500, 0.0030, timeToExp, 0.39], {stockPrice, 10, 1000}, {timetoExp, 0.0833333, 5}] Other plots, like this sample from the reference, do work. Plot3D[{x^2 + y^2, -x^2 - y^2}, {x, -2, 2}, {y, -2, 2}, RegionFunction -> Function[{x, y, z}, x^2 + y^2 <= 4], BoxRatios -> Automatic]

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• posmax: like argmax but gives the position(s) of the element x for which f[x] is maximal

  - by dreeves

  Mathematica has a built-in function ArgMax for functions over infinite domains, based on the standard mathematical definition. The analog for finite domains is a handy utility function. Given a function and a list (call it the domain of the function), return the element(s) of the list that maximize the function. Here's an example of finite argmax in action: http://stackoverflow.com/questions/471029/canonicalize-nfl-team-names/472213#472213 And here's my implementation of it (along with argmin for good measure): (* argmax[f, domain] returns the element of domain for which f of that element is maximal -- breaks ties in favor of first occurrence. *) SetAttributes[{argmax, argmin}, HoldFirst]; argmax[f_, dom_List] := Fold[If[f[#1]>=f[#2], #1, #2]&, First[dom], Rest[dom]] argmin[f_, dom_List] := argmax[-f[#]&, dom] First, is that the most efficient way to implement argmax? What if you want the list of all maximal elements instead of just the first one? Second, how about the related function posmax that, instead of returning the maximal element(s), returns the position(s) of the maximal elements?

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• Implementing IComparer<T> For IComparer<DictionaryEntry>

  - by Phil Sandler

  I am using the ObservableSortedDictionary from Dr. WPF. The constructor looks like this: public ObservableSortedDictionary(IComparer<DictionaryEntry> comparer) I am really struggling to create an implementation that satisfies the constructor and works. My current code (that won't compile) is: public class TimeCreatedComparer<T> : IComparer<T> { public int Compare(T x, T y) { var myclass1 = (IMyClass)((DictionaryEntry)x).Value; var myclass2 = (IMyClass)((DictionaryEntry)y).Value; return myclass1.TimeCreated.CompareTo(myclass2.TimeCreated); } } It says I can't cast from T to DictionaryEntry. If I cast directly to IMyClass, it compiles, but I get a runtime error saying I can't cast from DictionaryEntry to IMyClass. At runtime, x and y are instances of DictionaryEntry, which each have the correct IMyClass as their Value.

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• How to avoid having very large objects with Domain Driven Design

  - by Pablojim

  We are following Domain Driven Design for the implementation of a large website. However by putting the behaviour on the domain objects we are ending up with some very large classes. For example on our WebsiteUser object, we have many many methods - e.g. dealing with passwords, order history, refunds, customer segmentation. All of these methods are directly related to the user. Many of these methods delegate internally to other child object but this still results in some very large classes. I'm keen to avoid exposing lots of child objects e.g. user.getOrderHistory().getLatestOrder(). What other strategies can be used to avoid this problems?

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• JavaFX Threading issue - GUI freezing while method call ran.

  - by David Meadows

  Hi everyone, I hoped someone might be able to help as I'm a little stumped. I have a javafx class which runs a user interface, which includes a button to read some text out loud. When you press it, it invokes a Java object which uses the FreeTTS java speech synth to read out loud a String, which all works fine. The problem is, when the speech is being read out, the program stops completely until its completed. I'm not an expert on threaded applications, but I understand that usually if I extend the Thread class, and provided my implementation of the speech synth code inside an overridden run method, when I call start on the class it "should" create a new Thread, and run this code there, allowing the main thread which has the JavaFX GUI on to continue as normal. Any idea why this isn't the case? Thanks a lot in advance!

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• how start implement MVVM pattern

  - by netmajor

  Hello, So i decide to to develop my asp.net site into Silverlight. I today start to search articles about MVVM pattern which i want use in my Silverlight app, and i am confused :/ It's hart to me understand how works this pattern. I am find 3 frameworks which supports MVVM pattern in Silverlight - Caliburn, MVVM Light Toolkit and GoodLight. Should i start from own implementation of pattern or use framework? Is this frameworks only a project solutions in which i can insert my code? Which framework is the best for novice and which for professional? I ask for this, cause i must start to rewrite my app from asp.net to Silverlight and i don't know that i can do it first and later (when i understand MVVM pattern and framework) implement this pattern in finished app ? Or from begining rewrite project to MVVM framework?

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• Examining mmaped addresses using GDB

  - by Mikeage

  I'm using the driver I posted at http://stackoverflow.com/questions/647783/direct-memory-access-in-linux/ to mmap some physical ram into a userspace address. However, I can't use GDB to look at any of the address; i.e., x 0x12345678 (where 0x12345678 is the return value of mmap) fails with an error "Cannot access memory at address 0x12345678". Is there any way to tell GDB that this memory can be viewed? Alternatively, is there something different I can do in the mmap (either the call or the implementation of foo_mmap there) that will allow it to access this memory? Note that I'm not asking about /dev/mem (as in the first snippet there) but amount a mmap to memory acquired via ioremap(), virt_to_phys() and remap_pfn_range()

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• ICalendar parser in PHP that supports timezones

  - by Vincent Robert

  I am looking for a PHP class that can parse an ICalendar (ICS) file and correctly handle timezones. I already created an ICS parser myself but it can only handle timezones known to PHP (like 'Europe/Paris'). Unfortunately, ICS file generated by Evolution (default calendar software of Ubuntu) does not use default timezone IDs. It exports events with its a specific timezone ID exporting also the full definition of the timezone: daylight saving dates, recurrence rule and all the hard stuff to understand about timezones. This is too much for me. Since it was only a small utility for my girlfriend, I won't have time to investigate further the ICalendar specification and create a full blown ICalendar parser myself. So is there any known implementation in PHP of ICalendar file format that can parse timezones definitions?

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• viewDidLoad never called in Sub-classed UIViewController

  - by Steve

  I've run into some trouble with loading a sub-classed UIViewController from a nib. My viewDidLoad function is never called. The super-class has no nib, but the sub-classes each have their own. i.e. @interface SuperClass : UIViewController { } @end @interface SubClass : SuperClass{ } @end @implementation SubClass - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { } return self; } - (void)viewDidLoad{ // Never called } The view is loaded from a nib as follows: SubClass *scvc = [[SubClass alloc] initWithNibName:@"SubClass" bundle:nil]; [self.navigationController pushViewController:scvc animated:YES]; [scvc release]; There is a nib file with this name and it has it's file owner's class set properly. viewDidLoad is not called in the child or super. Any ideas?

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• Programmatically allow write access for a Registry key

  - by Kerido

  Hi everybody, I need to programmatically modify the Access Descriptors on a known Registry key during product installation. The way I want it to work is: The installer is run in Administrative mode. A Registry key is created. A function (the one I need) queries the ACL from the key. If this function finds that the group 'Users' already has write access, nothing should be done. If not, it should add a new permission allowing write access to the 'Users' group. The permissions are saved for the Registry key. This question is similar to Setting Registry key write permissions using .NET, however, I need a C++/Win32 implementation. Thanks in advance

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• XSLT good choice for web framework?

  - by Xepoch

  I've always thought of XML (and SGML before that) data as the devil's format. I'm of the old database and flat files school. Nonetheless, we are developing a commercially-available web product who's framework is based off of translating/transforming XML data in chains. As we're interviewing for positions as well talking to potential customers, they love the concept of what it will do but are weary of supporting XSLT long-term. One person even called it the proverbial "dead." Dead like COBOL, Unix, and C or dead like Apple Business BASIC? Anyway, I'm curious if building a web framework on XSLT is really not cutting edge enough (oddly) for companies. Are there inherent XSLT implementation problems that make this venture something worth reconsidering?

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• WCF Business logic handling

  - by Raj

  I have a WCF service that supports about 10 contracts, we have been supporting a client with all the business rules specific to this client now we have another client who will be using the exact same contracts (so we cannot change that) they will be calling the service exactly the same way the previous client called now the only way we can differentiate between the two clients is by one of the input parameters. Based on this input parameter we have to use a slightly different business logic – the logic for both the Client will be same 50% of the time the remainder will have different logic (across Business / DAL layers) . I don’t want to use if else statement in each of contract implementation to differentiate and reroute the logic also what if another client comes in. Is there a clean way of handling a situation like this. I am using framework 3.5. Like I said I cannot change any of the contracts (service / data contract ) or the current service calling infrastructure for the new client. Thanks

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• NHibernate session management in ASP.NET MVC

  - by Kevin Pang

  I am currently playing around with the HybridSessionBuilder class found on Jeffrey Palermo's blog post: http://jeffreypalermo.com/blog/use-this-nhibernate-wrapper-to-keep-your-repository-classes-simple/ Using this class, my repository looks like this: public class UserRepository : IUserRepository { private readonly ISessionBuilder _sessionBuilder; public UserRepository(ISessionBuilder sessionBuilder) { _sessionBuilder = sessionBuilder; } public User GetByID(string userID) { using (ISession session = _sessionBuilder.GetSession()) { return session.Get<User>(userID); } } } Is this the best way to go about managing the NHibernate session / factory? I've heard things about Unit of Work and creating a session per web request and flushing it at the end. From what I can tell, my current implementation isn't doing any of this. It is basically relying on the Repository to grab the session from the session factory and use it to run the queries. Are there any pitfalls to doing database access this way?

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• Refactor/rewrite code or continue?

  - by Dan

  I just completed a complex piece of code. It works to spec, it meets performance requirements etc etc but I feel a bit anxious about it and am considering rewriting and/or refactoring it. Should I do this (spending time that could otherwise be spent on features that users will actually notice)? The reasons I feel anxious about the code are: The class hierarchy is complex and not obvious Some classes don't have a well defined purpose (they do a number of unrelated things) Some classes use others internals (they're declared as friend classes) to bypass the layers of abstraction for performance, but I feel they break encapsulation by doing this Some classes leak implementation details (eg, I changed a map to a hash map earlier and found myself having to modify code in other source files to make the change work) My memory management/pooling system is kinda clunky and less-than transparent They look like excellent reasons to refactor and clean code, aiding future maintenance and extension, but could be quite time consuming. Also, I'll never be perfectly happy with any code I write anyway... So, what does stackoverflow think? Clean code or work on features?

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• Add XSLT 2 schema to Visual Studio 2010 for intellisense

  - by David Merrilees

  I'd like to add the XSLT 2 schema to Visual Studio 2010 to provide intellisense. I've added the schema to C:\Program Files\Microsoft Visual Studio 10.0\Xml\Schemas (removing the XSLT 1 schema), but to no avail. The schema seems to have been parsed by Visual Studio, as I can hover my cursor over the namespace declaration in the stylesheet (xmlns:xsl="http://www.w3.org/1999/XSL/Transform") and see the comments from the new schema, however, intellisense still refers to the XSLT 1 implementation. For example the element has a warning that 'xsl:function is not yet available'. Do I need to register the schema in some way? Any suggestions welcome.

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• Objective-C categories: Can I add a property for a method not in my category?

  - by Squeegy

  I want to use a category to make a method on the original class available as a property as well. Class A: @interface ClassA - (NSString*)foo; @end Class A category @interface ClassA (Properties) - (void)someCategoryMethod; @property (nonatomic, readonly) NSString *foo; @end Now when I do this, it seems to work, but it gives me warnings because I am not synthesizing the property in my category implementation. How do I tell the compiler everything is actually just fine since the original class synthesizes the property for me?

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