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• What software analogies have helped you?

  - by Galwegian

  I have often enjoyed the use of analogies in understanding a software scenario or problem. For example, to understand the concept of public key encryption, the 'locked mailbox' analogy or similar is often used as an aid: An analogy for public-key encryption is that of a locked mailbox with a mail slot. The mail slot is exposed and accessible to the public; its location (the street address) is in essence the public key. Anyone knowing the street address can go to the door and drop a written message through the slot; however, only the person who possesses the key can open the mailbox and read the message. My question is: What analogies have you used or heard of in your career that have given you that "Eureka" moment with a complex concept? EDIT: If you have a good one, don't just state the name, please share with the group!

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• Preserving original StackTrace/LineNumbers in .NET Exceptions

  - by Sam

  Understanding the difference between throw ex and throw, why is the original StackTrace preserved in this example: static void Main(string[] args) { try { LongFaultyMethod(); } catch (System.Exception ex) { Console.WriteLine(ex.StackTrace); } } static void LongFaultyMethod() { try { int x = 20; SomethingThatThrowsException(x); } catch (Exception) { throw; } } static void SomethingThatThrowsException(int x) { int y = x / (x - x); } But not in this one: static void Main(string[] args) { try { LongFaultyMethod(); } catch (System.Exception ex) { Console.WriteLine(ex.StackTrace); } } static void LongFaultyMethod() { try { int x = 20; int y = x / (x - 20); } catch (Exception) { throw; } } The second scenario is producing the same output as throw ex would? In both cases, one expects to see the line number where y is initialized.

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• tool for adding parentheses to equations?

  - by jedierikb

  Is there an online tool for adding parentheses to simple math equations? For example, a + b * c into a + (b * c) Those who paid more attention in math class might be able to tackle order of operations for huge equations in their head, but I could often use some help (and verification of my thinking). I often encounter other people's libraries having equations and functions I need for my code, and this would be kind of helpful for debugging and understanding. I was hoping Wolfram Alpha would do this, but the output is not easy to plug back into most programming languages e.g. a + (bc)

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• JPanel: both implementing my own paintComponent() and rendering children doesn't work

  - by Paul Marshall

  I'm extending a JPanel to display a game board, and adding a JEditorPane at the bottom to hold some status text. Unfortunately, the game board renders just fine, but the JEditorPane is just a blank gray area until I highlight the text in it, when it will render whatever text is highlighted (but not the rest). If I'm understanding Swing right, it should work, because super.paintComponent(g) should render the other children (i.e., the JEditorPane). Tell me, o great stackoverflow, what bonehead mistake am I making? public GameMap extends JPanel { public GameMap() { JEditorPane statusLines = new JEditorPane("text/plain","Stuff"); this.setLayout(new BoxLayout(this,BoxLayout.PAGE_AXIS)); this.add(new Box.Filler(/*enough room to draw my game board*/)); this.add(statusLines); } public void paintComponent(Graphics g){ super.paintComponent(g); for ( all rows ){ for (all columns){ //paint one tile } } } }

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• EXC_BAD_ACCESS when not using self.

  - by chris

  I got nabbed by the following bug again and would like some clarification to exactly why it is a bug. I have a simple UITableView that loads some data: // myclass.h @property (nonatomic, retain) NSArray *myData // myclass.m @synthesize myData; - (void) viewDidLoad { ... myData = someDataSource // note the lack of self } - (UITableViewCell *) cellForRowAtIndexPath ... { ... cell.textLabel.text = [self.myData objectAtIndex:indexPath.row]; // EXC_BAD_ACCESS } The table first loads fine, but when scrolling up enough that one of the cells is totally out of the view I then get the EXC_BAD_ACCESS error. Am I missing something in regards to @property retain. My understanding is that it releases anything that the pointer was previously pointing to before the reassignment. If I am correct then why would not using self. cause any problems? Thanks for the help.

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• Good learning resources for JNDI implementation (JBoss 5)

  - by iandisme

  I have been working with JavaEE/EJB3 web apps for about half a year now. Until recently, I haven't had to touch a lot of the behind-the-scenes stuff, just the meat of the code. I have been wrestling with JNDI problems, and though I've solved a couple of them, I'm pretty much just doing the whole cargo cult copy-paste routine. It would really help me to better understand JNDI; my understanding of it right now can be summarized as "it's that thing these classes sometimes do to find other classes." My question is, has anyone had success learning JNDI/EJB3/related topics from a book or online content? I've googled for it but the stuff that comes up is old or specific to a certain framework I'm not using. I'm looking for something that's either JBoss-specific or generic enough to be useful anyway.

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• Entity Framework VS LINQ to SQL VS ADO.NET with stored procedures?

  - by BritishDeveloper

  How would you rate each of them in terms of: Performance Speed of development Neat, intuitive, maintainable code Flexibility Overall I like my SQL and so have always been a die-hard fan of ADO.NET and stored procedures but I recently had a play with Linq to SQL and was blown away by how quickly I was writing out my DataAccess layer and have decided to spend some time really understanding either Linq to SQL or EF... or neither? I just want to check, that there isn't a great flaw in any of these technologies that would render my research time useless. E.g. performance is terrible, it's cool for simple apps but can only take you so far

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• How do I create queries to SQL Server tables via Visual Studio when no knowledge about SQL nor Linq?

  - by Kent S. Clarkson

  Let´s be frank, my knowledge regarding SQL language is very low. Nevertheless, my boss gave me the task to build a database application using the following tools: SQL Server and Visual Studio 2008; C#. I use the VS DataSet as a local mirror of the SQL Server. And let´s be frank again, my understanding of the VS Query builder is also very small, I´m finding it quite confusing, actually. So no help to find from Query builder. And my knowledge of Linq is even lower... Perhaps I should mention that the deadline for the project is "aggressively" set, so I have no chance to learn enough about these things during the project. And I´m a bit stupid too, which is no help when it comes to challenges like this (on other occations it might be quite useful though) With these permissions, what should I do (except for killing myself or retire) to be able to query my tables in a sufficient way?

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• Java: Best practices for turning foreign horror-code into clean API...?

  - by java.is.for.desktop

  Hello, everyone! I have a project (related to graph algorithms). It is written by someone else. The code is horrible: public fields, no getters/setters huge methods, all public some classes have over 20 fields some classes have over 5 constructors (which are also huge) some of those constructors just left many fields null (so I can't make some fields final, because then every second constructor signals errors) methods and classes rely on each other in both directions I have to rewrite this into a clean and understandable API. Problem is: I myself don't understand anything in this code. Please give me hints on analyzing and understanding such code. I was thinking, perhaps, there are tools which perform static code analysis and give me call graphs and things like this.

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• What exactly is a Monad?

  - by WeNeedAnswers

  Can someone please explain to me what a Monad is. I think I grasp Monoids and I grasp that they basically control the input of state into a system. I just look at the text in Haskell and glaze over. A simple example in python would be great. My current understanding is that a Monoid is a procedural piece of code that needs to be read from top to bottom in sequence with the output being the input for the function. I think that I may even got that wrong, but hey I am here to learn.

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• convert int to string for use in allegro function

  - by ace

  I am trying to run the following code using allegro. textout_ex(screen, font, numbComments , 100, 100, GREEN, BLACK); numbComments is an integer, the function prototype of this function is void textout_ex(BITMAP *bmp, const FONT *f, const char *s, int x, int y, int color, int bg); and i cannot, according to my understanding pass this integer in the third position. I therefore need to convert the integer into a string. I did it like this, but it didnt work. Help please? int score = numbComments; string Str; stringstream out; // YOU MUST INCLUDE <sstream> FOR THIS. out << score; Str = out.str(); and then tried to use the string Str, which didnt work

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• How to determine whether a .NET exception is being handled?

  - by romkyns

  We're investigating a coding pattern in C# in which we'd like to use a "using" clause with a special class, whose Dispose() method does different things depending on whether the "using" body was exited normally or with an exception. To the best of my understanding, the CLR keeps track of the current exception being handled until it's been consumed by a "catch" handler. However it's not entirely clear whether this information is exposed in any way for the code to access. Do you know whether it is, and if so, how to access it? For example: using (var x = new MyObject()) { x.DoSomething(); x.DoMoreThings(); } class MyObject : IDisposable { public void Dispose() { if (ExceptionIsBeingHandled) Rollback(); else Commit(); } } This looks almost like System.Transactions.TransactionScope, except that success/failure is not determined by a call to x.Complete(), but rather based on whether the using body was exited normally.

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• LAMP Stack with APC installed - WordPress Site - Is WP opcode being cached with APC?

  - by Christopher Altman

  I have a LAMP stack with APC installed. I have a WordPress site on this server. Is WP taking advantage of the opcode caching? I have done no WP configurations. My understanding is that simply having APC installed means that all PHP code is being cached. If that is untrue, please point me to the direction where I can configure WP to take advantage of APC. Note: I thought about this as a ServerFault question, but since the solution to is code related I posted on Stackoverflow.

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• jquery atrr("href") is not consistent ..in sharepoint

  - by alienavatar

  Hi all I have a jquery function(This is not written by me anyway still I am learning). In that we are replacing urls using f.attr("href") in several places. I am not understanding that from where this href value will be binded. And why the value(f.attr("href")) is changing place to place. I mean to say it is having some value @ one location and if I give the same it is giving me different value at other location. I read in article that The .attr() method gets the attribute value for only the first element in the matched set..What is the matched set means

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• iPhone: Cannot get simulator to generate .gcda profiling data files.

  - by Derek Clarkson

  I'm attempting to profile my code using the iPhone simulator. I've enabled Generate Test Coverage File and Instrument Program Flow and added -lgcov to the linker flags. According to everything I've read that should be all I need to do in terms of setup. Executing the program I can see the .gcno files appearing along side the .o compiled code in the build/.build/Debug-iphonesimulator/.build/Objects-normal/i386 directory. But when I run the app in the simulator I do not get any *.gcda files appearing. My understanding is that these files contain the data from the instrumentation. But I cannot find them anywhere on the computer. I know they can be produced and appear along side the *.gcno files because I have an old trashed buil directory which does have them. I just cannot figure out what I have to do to get them to appear and record the run. Any help appreciated.

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• is there a downside to putting N in front of strings in scripts? Is it considered a "best practice"?

  - by jcollum

  Let's say I have a table that has a varchar field. If I do an insert like this: INSERT MyTable SELECT N'the string goes here' Is there any fundamental difference between that and: INSERT MyTable SELECT 'the string goes here' My understanding was that you'd only have a problem if the string contained a Unicode character and the target column wasn't unicode. Other than that, SQL deals with it just fine and converts the string with the N'' into a varchar field (basically ignores the N). I was under the impression that N in front of strings was a good practice, but I'm unable to find any discussion of it that I'd consider definitive. Title may need improvement, feel free.

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• Grails / GORM, Disable First-level Cache

  - by Stephen Swensen

  Suppose I have the following Domain class mapping to a legacy table, utilizing read-only second-level cache, and having a transient field: class DomainObject { static def transients = ['userId'] Long id Long userId static mapping = { cache usage: 'read-only' table 'SOME_TABLE' } } I have a problem, references to DomainObject are being shared due to first-level caching, and thus transient fields are writing over each other. For example, def r1 = DomainObject.get(1) r1.userId = 22 def r2 = DomainObject.get(1) r2.userId = 34 assert r1.userId == 34 That is, r1 and r2 are references to the same instance. This is undesirable, I would like to cache the table data without sharing references. Any ideas? [Edit] Understanding the situation better now, I believe my question boils down to the following: Is there anyway to disable first level cache for a specific domain class while still using second level cache?

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• What simple methods are there to wrap a c++ based object model with a COM interface

  - by Rich

  I have a pre-existing c++ object model which represents the business layer tier of an application. I want to be able to expose the object model to applications written in other languages i.e vbscript, VB, javascript etc. I believe the best way of doing this is to wrap the business objects with a COM layer. What fast and effective methods are there for doing this. Any advice, links to practical "How to" documentation would be very much appreciated. Because I'm starting a bounty on this , here's a few extra guidelines for potential bounty hunters :- 1)I've decided on an ATL approach 2)I'm now specifically looking for links to really good "how to and quickly" documentation on wrapping a pre-existing c++ object model to make it useable by a scripting language like javascript 3) Something with small working examples showing me what code needs to be added to what files, e.g what goes into the cpp , idl and hpp/h etc. It' must include an example I can compile test and change to get a better understanding.

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• Are Scala "continuations" just a funky syntax for defining and using Callback Functions?

  - by Alex R

  And I mean that in the same sense that a C/Java for is just a funky syntax for a while loop. I still remember when first learning about the for loop in C, the mental effort that had to go into understanding the execution sequence of the three control expressions relative to the loop statement. Seems to me the same sort of effort has to be applied to understand Continuations (in Scala and I guess probably other languages). And then there's the obvious follow-up question... if so, then what's the point? It seems like a lot of pain (language complexity, programmer errors, unreadable programs, etc) for no gain.

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• how to pass an arbitrary signature to Certifcate

  - by eskoba

  I am trying to sign certificate (X509) using secret sharing. that is shareholders combine their signatures to produce the final signature. which will be in this case the signed certificate. however practically from my understanding only one entity can sign a certificate. therefore I want to know: which entities or data of the x509certificate are actually taken as input to the signing algorithm? ideally I want this data to be signed by the shareholders and then the final combination will be passed to the X509certificate as valid signature. is this possible? how could it done? if not are they other alternatives?

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• What is the difference between MVC model 1 and model 2?

  - by Alex Ciminian

  I've recently discovered that MVC is supposed to have two different flavors, model one and model two. I'm supposed to give a presentation on MVC1 and I was instructed that "it's not the web based version, that is refered to as MVC2". As the presentations are about design patterns in general, I doubt that this separation is related to Java (I found some info on Sun's site, but it seemed far off) or ASP. I have a pretty good understanding of what MVC is and I've used several (web) frameworks that enforce it, but this terminology is new to me. How is the web-based version different from other MVC (I'm guessing GUI) implementations? Does it have something to do with the stateless nature of HTTP? Thanks, Alex

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• What is the JavaScript variable scope in a switch / case statment?

  - by Todd Moses

  While creating JavaScript with ASP.NET MVC I noticed several scope warnings and realized that I am missing something with understanding the variable scope inside the switch / case statement. Warning: 'i' is already defined referring to case b and case c My code looks similar to this: switch(element) { case 'a': for(var i=0; i < count; i++){ do something } break; case 'b': for(var i=0; i < count; i++){ do something } break; case 'c': for(var i=0; i < count; i++){ do something } break; } I thought scope ended with each break statement but it seems that scope does not end until the end of the switch/case. Is scope for the entire switch/case?

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• setting url in yaml file for google app engin (page not found) problem

  - by mswallace

  I am new to python and I am super excited to learn. I am building my first app on app engin and I am not totally understanding why my yaml file is not resolving to the url that I set up. here is the code handlers: - url: .* script: main.py - url: /letmein/.* script: letmein.py so if I go to http://localhost:8080/letmein/ I get a link is brooken or page not found error. here is the python code that I have in letmein.py from google.appengine.ext import webapp from google.appengine.ext.webapp import util class LetMeInHandler(webapp.RequestHandler): def get(self): self.response.out.write('letmein!') def main(): application = webapp.WSGIApplication([('/letmein/', LetMeInHandler)], debug=True) util.run_wsgi_app(application) if __name__ == '__main__': main() thanks in advance for the help!

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• I need help translating this portion of the ECMAScript grammar?

  - by ChaosPandion

  I've been working on my own implementation of ECMAScript for quite some time now. I have basically done everything by hand to help gain a deep understanding of the process. Repeated attempts to analyze and understand this portion of the grammar have failed so I've been working on the run time instead. Now I am at a point were I will be working on object literals so I really need to polish my syntactic analyzer. Can anyone put this in terms a language parser novice could understand? My biggest source of confusion is the following: new MemberExpression Arguments This is supposed to be a member expression, but this seemingly conflicts with the following: NewExpression : MemberExpression new NewExpression Is a new expression a member expression or a left hand side expression? To be honest I am having trouble laying out the proper C# classes for the concrete grammar. MemberExpression : PrimaryExpression FunctionExpression MemberExpression [ Expression ] MemberExpression . IdentifierName new MemberExpression Arguments NewExpression : MemberExpression new NewExpression CallExpression : MemberExpression Arguments CallExpression Arguments CallExpression [ Expression ] CallExpression . IdentifierName LeftHandSideExpression : NewExpression CallExpression

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• how to pass in dynamic data to decorators

  - by steve

  Hi, I am trying to write a base crud controller class that does the following: class BaseCrudController: model = "" field_validation = {} template_dir = "" @expose(self.template_dir) def new(self, *args, **kwargs) .... @validate(self.field_validation, error_handler=new) @expose() def post(self, *args, **kwargs): ... My intent is to have my controllers extend this base class, set the model, field_validation, and template locations, and am ready to go. Unfortunately, decorators (to my understanding), are interpreted when the function is defined. Hence it won't have access to instance's value. Is there a way to pass in dynamic data or values from the sub class? If not, I guess I could use override_template as a workaround to expose and set the template within the controller action. How would I go about validating the form within the controller action? Thanks, Steve

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