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• The Evolution Of C#

  - by Paulo Morgado

  The first release of C# (C# 1.0) was all about building a new language for managed code that appealed, mostly, to C++ and Java programmers. The second release (C# 2.0) was mostly about adding what wasn’t time to built into the 1.0 release. The main feature for this release was Generics. The third release (C# 3.0) was all about reducing the impedance mismatch between general purpose programming languages and databases. To achieve this goal, several functional programming features were added to the language and LINQ was born. Going forward, new trends are showing up in the industry and modern programming languages need to be more: Declarative With imperative languages, although having the eye on the what, programs need to focus on the how. This leads to over specification of the solution to the problem in hand, making next to impossible to the execution engine to be smart about the execution of the program and optimize it to run it more efficiently (given the hardware available, for example). Declarative languages, on the other hand, focus only on the what and leave the how to the execution engine. LINQ made C# more declarative by using higher level constructs like orderby and group by that give the execution engine a much better chance of optimizing the execution (by parallelizing it, for example). Concurrent Concurrency is hard and needs to be thought about and it’s very hard to shoehorn it into a programming language. Parallel.For (from the parallel extensions) looks like a parallel for because enough expressiveness has been built into C# 3.0 to allow this without having to commit to specific language syntax. Dynamic There was been lots of debate on which ones are the better programming languages: static or dynamic. The fact is that both have good qualities and users of both types of languages want to have it all. All these trends require a paradigm switch. C# is, in many ways, already a multi-paradigm language. It’s still very object oriented (class oriented as some might say) but it can be argued that C# 3.0 has become a functional programming language because it has all the cornerstones of what a functional programming language needs. Moving forward, will have even more. Besides the influence of these trends, there was a decision of co-evolution of the C# and Visual Basic programming languages. Since its inception, there was been some effort to position C# and Visual Basic against each other and to try to explain what should be done with each language or what kind of programmers use one or the other. Each language should be chosen based on the past experience and familiarity of the developer/team/project/company and not by particular features. In the past, every time a feature was added to one language, the users of the other wanted that feature too. Going forward, when a feature is added to one language, the other will work hard to add the same feature. This doesn’t mean that XML literals will be added to C# (because almost the same can be achieved with LINQ To XML), but Visual Basic will have auto-implemented properties. Most of these features require or are built on top of features of the .NET Framework and, the focus for C# 4.0 was on dynamic programming. Not just dynamic types but being able to talk with anything that isn’t a .NET class. Also introduced in C# 4.0 is co-variance and contra-variance for generic interfaces and delegates. Stay tuned for more on the new C# 4.0 features.

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• Hidden Features of C#?

  - by Serhat Özgel

  This came to my mind after I learned the following from this question: where T : struct We, C# developers, all know the basics of C#. I mean declarations, conditionals, loops, operators, etc. Some of us even mastered the stuff like Generics, anonymous types, lambdas, linq, ... But what are the most hidden features or tricks of C# that even C# fans, addicts, experts barely know? Here are the revealed features so far: Keywords yield by Michael Stum var by Michael Stum using() statement by kokos readonly by kokos as by Mike Stone as / is by Ed Swangren as / is (improved) by Rocketpants default by deathofrats global:: by pzycoman using() blocks by AlexCuse volatile by Jakub Šturc extern alias by Jakub Šturc Attributes DefaultValueAttribute by Michael Stum ObsoleteAttribute by DannySmurf DebuggerDisplayAttribute by Stu DebuggerBrowsable and DebuggerStepThrough by bdukes ThreadStaticAttribute by marxidad FlagsAttribute by Martin Clarke ConditionalAttribute by AndrewBurns Syntax ?? operator by kokos number flaggings by Nick Berardi where T:new by Lars Mæhlum implicit generics by Keith one-parameter lambdas by Keith auto properties by Keith namespace aliases by Keith verbatim string literals with @ by Patrick enum values by lfoust @variablenames by marxidad event operators by marxidad format string brackets by Portman property accessor accessibility modifiers by xanadont ternary operator (?:) by JasonS checked and unchecked operators by Binoj Antony implicit and explicit operators by Flory Language Features Nullable types by Brad Barker Currying by Brian Leahy anonymous types by Keith __makeref __reftype __refvalue by Judah Himango object initializers by lomaxx format strings by David in Dakota Extension Methods by marxidad partial methods by Jon Erickson preprocessor directives by John Asbeck DEBUG pre-processor directive by Robert Durgin operator overloading by SefBkn type inferrence by chakrit boolean operators taken to next level by Rob Gough pass value-type variable as interface without boxing by Roman Boiko programmatically determine declared variable type by Roman Boiko Static Constructors by Chris Easier-on-the-eyes / condensed ORM-mapping using LINQ by roosteronacid Visual Studio Features select block of text in editor by Himadri snippets by DannySmurf Framework TransactionScope by KiwiBastard DependantTransaction by KiwiBastard Nullable<T> by IainMH Mutex by Diago System.IO.Path by ageektrapped WeakReference by Juan Manuel Methods and Properties String.IsNullOrEmpty() method by KiwiBastard List.ForEach() method by KiwiBastard BeginInvoke(), EndInvoke() methods by Will Dean Nullable<T>.HasValue and Nullable<T>.Value properties by Rismo GetValueOrDefault method by John Sheehan Tips & Tricks nice method for event handlers by Andreas H.R. Nilsson uppercase comparisons by John access anonymous types without reflection by dp a quick way to lazily instantiate collection properties by Will JavaScript-like anonymous inline-functions by roosteronacid Other netmodules by kokos LINQBridge by Duncan Smart Parallel Extensions by Joel Coehoorn

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• Java RegEx API "Look-behind group does not have an obvious maximum length near index ..."

  - by Foo Inc

  Hello, I'm on to some SQL where clause parsing and designed a working RegEx to find a column outside string literals using "Rad Software Regular Expression Desginer" which is using the .NET API. To make sure the designed RegEx works with Java too, I tested it by using the API of course (1.5 and 1.6). But guess what, it won't work. I got the message "Look-behind group does not have an obvious maximum length near index 28". The string that I'm trying to get parsed is Column_1='test''the''stuff''all''day''long' AND Column_2='000' AND TheVeryColumnIWantToFind = 'Column_1=''test''''the''''stuff''''all''''day''''long'' AND Column_2=''000'' AND TheVeryColumnIWantToFind = '' TheVeryColumnIWantToFind = '' AND (Column_3 is null or Column_3 = ''Not interesting'') AND ''1'' = ''1''' AND (Column_3 is null or Column_3 = 'Still not interesting') AND '1' = '1' As you may have guessed, I tried to create some kind of worst case to ensure the RegEx won't fail on more complicated SQL where clauses. The RegEx itself looks like this (?i:(?<!=\s*'(?:[^']|(?:''))*)((?<=\s*)TheVeryColumnIWantToFind(?=(?:\s+|=)))) I'm not sure if there is a more elegant RegEx (there'll most likely be one), but that's not important right now as it does the trick. To explain the RegEx in a few words: If it finds the column I'm after, it does a negative look-behind to figure out if the column name is used in a string literal. If so, it won't match. If not, it'll match. Back to the question. As I mentioned before, it won't work with Java. What will work and result in what I want? I found out, that Java does not seem to support unlimited look-behinds but still I couldn't get it to work. Isn't it right that a look-behind is always putting a limit up on itself from the search offset to the current search position? So it would result in something like "position - offset"?

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• ANTLR AST rules fail with RewriteEmptyStreamException

  - by Barry Brown

  I have a simple grammar: grammar sample; options { output = AST; } assignment : IDENT ':=' expr ';' ; expr : factor ('*' factor)* ; factor : primary ('+' primary)* ; primary : NUM | '(' expr ')' ; IDENT : ('a'..'z')+ ; NUM : ('0'..'9')+ ; WS : (' '|'\n'|'\t'|'\r')+ {$channel=HIDDEN;} ; Now I want to add some rewrite rules to generate an AST. From what I've read online and in the Language Patterns book, I should be able to modify the grammar like this: assignment : IDENT ':=' expr ';' -> ^(':=' IDENT expr) ; expr : factor ('*' factor)* -> ^('*' factor+) ; factor : primary ('+' primary)* -> ^('+' primary+) ; primary : NUM | '(' expr ')' -> ^(expr) ; But it does not work. Although it compiles fine, when I run the parser I get a RewriteEmptyStreamException error. Here's where things get weird. If I define the pseudo tokens ADD and MULT and use them instead of the tree node literals, it works without error. tokens { ADD; MULT; } expr : factor ('*' factor)* -> ^(MULT factor+) ; factor : primary ('+' primary)* -> ^(ADD primary+) ; Alternatively, if I use the node suffix notation, it also appears to work fine: expr : factor ('*'^ factor)* ; factor : primary ('+'^ primary)* ; Is this discrepancy in behavior a bug?

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• Is VB Really Case Insensitive?

  - by Otaku

  I'm not trying to start an argument here, but for whatever reason it's typically stated that VB is case insensitive and C languages aren't (and somehow that is a good thing). But here's my question: Where exactly is VB case insensitive? When I type... Dim ss As String Dim SS As String ...into the VS2008 IDE the second one has a warning of "Local variable 'SS' is already declared in the current block". In VBA VBE, it doesn't immediately kick an error, but rather just auto-corrects the case. Am I missing something here with this argument that VB is not case sensitive? (Also, if you know or care to answer, why would that be a bad thing?) EDIT: Why am I even asking this question? I've used VB in many of it's dialects for years now, sometimes as a hobbyist, sometimes for small business-related programs in a workgroup. As of the last 6 months I've been working on a big project, much bigger than I anticipated. Much of the sample source code out there is in C#. I don't have any burning desire to learn C#, but if there are things I'm missing out on that C# offers that VB doesn't (an opposite would be VB.NET offers XML Literals), then I'd like to know more about that feature. So in this case, it's often argued that C languages are case sensitive and that's good and VB is case insensitive and that is bad. I'd like to know A) how exactly is VB case insensitive because every single example in the code editor becomes case sensititive (meaning case gets corrected) whether I want it or not and B) is this compelling enough for me to consider moving to C# if VB.NET case is somehow limiting what I could do with code?

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• Hidden features of Perl?

  - by Adam Bellaire

  What are some really useful but esoteric language features in Perl that you've actually been able to employ to do useful work? Guidelines: Try to limit answers to the Perl core and not CPAN Please give an example and a short description Hidden Features also found in other languages' Hidden Features: (These are all from Corion's answer) C# Duff's Device Portability and Standardness Quotes for whitespace delimited lists and strings Aliasable namespaces Java Static Initalizers JavaScript Functions are First Class citizens Block scope and closure Calling methods and accessors indirectly through a variable Ruby Defining methods through code PHP Pervasive online documentation Magic methods Symbolic references Python One line value swapping Ability to replace even core functions with your own functionality Other Hidden Features: Operators: The bool quasi-operator The flip-flop operator Also used for list construction The ++ and unary - operators work on strings The repetition operator The spaceship operator The || operator (and // operator) to select from a set of choices The diamond operator Special cases of the m// operator The tilde-tilde "operator" Quoting constructs: The qw operator Letters can be used as quote delimiters in q{}-like constructs Quoting mechanisms Syntax and Names: There can be a space after a sigil You can give subs numeric names with symbolic references Legal trailing commas Grouped Integer Literals hash slices Populating keys of a hash from an array Modules, Pragmas, and command-line options: use strict and use warnings Taint checking Esoteric use of -n and -p CPAN overload::constant IO::Handle module Safe compartments Attributes Variables: Autovivification The $[ variable tie Dynamic Scoping Variable swapping with a single statement Loops and flow control: Magic goto for on a single variable continue clause Desperation mode Regular expressions: The \G anchor (?{}) and '(??{})` in regexes Other features: The debugger Special code blocks such as BEGIN, CHECK, and END The DATA block New Block Operations Source Filters Signal Hooks map (twice) Wrapping built-in functions The eof function The dbmopen function Turning warnings into errors Other tricks, and meta-answers: cat files, decompressing gzips if needed Perl Tips See Also: Hidden features of C Hidden features of C# Hidden features of C++ Hidden features of Java Hidden features of JavaScript Hidden features of Ruby Hidden features of PHP Hidden features of Python

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• Where my memory is alloced, Stack or Heap, Can I find it at Run-time?

  - by AKN

  I know that memory alloced using new, gets its space in heap, and so we need to delete it before program ends, to avoid memory leak. Let's look at this program... Case 1: char *MyData = new char[20]; _tcscpy(MyData,"Value"); . . . delete[] MyData; MyData = NULL; Case 2: char *MyData = new char[20]; MyData = "Value"; . . . delete[] MyData; MyData = NULL; In case 2, instead of allocating value to the heap memory, it is pointing to a string literal. Now when we do a delete it would crash, AS EXPECTED, since it is not trying to delete a heap memory. Is there a way to know where the pointer is pointing to heap or stack? By this the programmer Will not try to delete any stack memory He can investigate why does this ponter, that was pointing to a heap memory initially, is made to refer local literals? What happened to the heap memory in the middle? Is it being made to point by another pointer and delete elsewhere and all that?

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• DIY intellisense on XPath - design approach? (WinForms app)

  - by Cheeso

  I read the DIY Intellisense article on code project, which was referenced from the Mimic Intellisense? question here on SO. I wanna do something similar, DIY intellisense, but for XPath not C#. The design approach used there makes sense to me: maintain a tree of terms, and when the "completion character" is pressed, in the case of C#, a dot, pop up the list of possible completions in a textfield. Then allow the user to select a term from the textfield either through typing, arrow keys, or double-click. How would you apply this to XPath autocompletion? should there be an autocomplete key? In XPath there is no obvious separator key like "dot" in C#. should the popup be triggered explicitly in some other way, let's say ctrl-. ? or should the parser try to autocomplete continuously? If I do the autocomplete continuously, how to scale it properly? There are 93 xpath functions, not counting overloads. I certainly don't want to popup a list of 93 choices. How do I decide when I've narrowed it enough to offer a useful lsit of possible completions? How to populate the tree of possible completions? For C#, it's easy: walk the type space via reflection. At a first level, the "syntax tree" for C# seems like a single tree, and the list of completions at any point depends on the graph of nodes you've traversed to that point. Typing System.Console. traverses to a certain node in that tree, and the list of completions is the set of child nodes available at that node in the tree. On the other hand, the xpath syntax seems like it is a "flatter" tree - function names, axis names, literals. Does this make sense? what have I not considered?

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• What's the compelling reason to upgrade to Visual Studio 2010 from VS2008?

  - by Cheeso

  Are there new features in Visual Studio 2010 that are must-haves? If so, which ones? For me, the big draws for VS2008 as compared to VS2005 were LINQ, .NET Framework multitargeting, WCF (REST + Syndication), and general devenv.exe reliability. Granted, some of these features are framework things, and not tool things. For the purposes of this discussion, I'm willing to combine them into one bucket. What is the list of must-have features for VS2010 versus VS2008? Are there any? I am particularly interested in C#. Update: I know how to google, so I can get the official list from Microsoft. I guess what I really wanted was, the assessment from people using it, as to which things are really notable. Microsoft went on for 3 pages about 2008/3.5 features, and many people sort of boiled it down to LINQ, and a few other things. What is that short list for VS2010? Summary so far, what people think is cool or compelling: Visual Studio engine multi-monitor support new extensibility model based on WPF, prettier and more usable new TFS stuff, incl automated test tools parallel debugging .NET Framework parallel extensions for .NET C# 4.0 generic variance optional and named params easier interop with non-managed environments, like COM or Javascript VB 10.0 collection and array literals / initializers automatic properties anonymous methods / statement lambdas I read up on these at Zander's blog. He described these and other features. Nobody on this list said anything about: Visual Studio engine F# support Javascript code-completion JQuery is now included UML better Sharepoint capabilities C++ moves to msbuild project files

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• constructor function's object literal returns toString() method but no other method

  - by JohnMerlino

  I'm very confused with javascript methods defined in objects and the "this" keyword. In the below example, the toString() method is invoked when Mammal object instantiated: function Mammal(name){ this.name=name; this.toString = function(){ return '[Mammal "'+this.name+'"]'; } } var someAnimal = new Mammal('Mr. Biggles'); alert('someAnimal is '+someAnimal); Despite the fact that the toString() method is not invoked on the object someAnimal like this: alert('someAnimal is '+someAnimal.toString()); It still returns 'someAnimal is [Mammal "Mr. Biggles"]' . That doesn't make sense to me because the toString() function is not being called anywhere. Then to add even more confusion, if I change the toString() method to a method I make up such as random(): function Mammal(name){ this.name=name; this.random = function(){ return Math.floor(Math.random() * 15); } } var someAnimal = new Mammal('Mr. Biggles'); alert(someAnimal); It completely ignores the random method (despite the fact that it is defined the same way was the toString() method was) and returns: [object object] Another issue I'm having trouble understanding with inheritance is the value of "this". For example, in the below example function person(w,h){ width.width = w; width.height = h; } function man(w,h,s) { person.call(this, w, h); this.sex = s; } "this" keyword is being send to the person object clearly. However, does "this" refer to the subclass (man) or the super class (person) when the person object receives it? Thanks for clearing up any of the confusion I have with inheritance and object literals in javascript.

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• An Ideal Keyboard Layout for Programming

  - by Jon Purdy

  I often hear complaints that programming languages that make heavy use of symbols for brevity, most notably C and C++ (I'm not going to touch APL), are difficult to type because they require frequent use of the shift key. A year or two ago, I got tired of it myself, downloaded Microsoft's Keyboard Layout Creator, made a few changes to my layout, and have not once looked back. The speed difference is astounding; with these few simple changes I am able to type C++ code around 30% faster, depending of course on how hairy it is; best of all, my typing speed in ordinary running text is not compromised. My questions are these: what alternate keyboard layouts have existed for programming, which have gained popularity, are any of them still in modern use, do you personally use any altered layout, and how can my layout be further optimised? I made the following changes to a standard QWERTY layout. (I don't use Dvorak, but there is a programmer Dvorak layout worth mentioning.) Swap numbers with symbols in the top row, because long or repeated literal numbers are typically replaced with named constants; Swap backquote with tilde, because backquotes are rare in many languages but destructors are common in C++; Swap minus with underscore, because underscores are common in identifiers; Swap curly braces with square brackets, because blocks are more common than subscripts; and Swap double quote with single quote, because strings are more common than character literals. I suspect this last is probably going to be the most controversial, as it interferes the most with running text by requiring use of shift to type common contractions. This layout has significantly increased my typing speed in C++, C, Java, and Perl, and somewhat increased it in LISP and Python.

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• Returning an array of culture formatted dates C# MVC3

  - by user1875797

  I'm new to programming and trying to do an exercise that formats a date to the Thai culture in a variety of formats this is what I have for my code so far: public String[] FormatAsSpecified(DateTime theDate, String theCulture, String[] formats) { String[] dateResults = new String[formats.Length]; CultureInfo culture = CultureInfo.GetCultureInfo(theCulture); for (int i = 0; i < formats.Length; i++) { String culture_formatted_date = theDate.ToString(formats[i], culture); dateResults[i] = culture_formatted_date; } return dateResults; } This is the test method that goes with it: [TestMethod] public void FormatAsSpecifiedReturnsDateLiteralsInSpecifiedFormatForAllStandardFormatStrings() { //Arrange var controller = new DateController(); var theDate = new DateTime(2014, 2, 14, 9, 15, 32, 376); String theCulture = "th-TH"; // Array of all supported standard date and time format specifiers. String[] formats = { "d", "D", "f", "F", "g", "G", "m", "o", "r", "s", "t", "T", "u", "U", "Y" }; //Corresponding date literals for the standard Thai regional settings String[] expectedResults = {"14/2/2557" , "14 ?????????? 2557" , "14 ?????????? 2557 9:15" , "14 ?????????? 2557 9:15:32" , "14/2/2557 9:15" , "14/2/2557 9:15:32" , "14 ??????????" , "2014-02-14T09:15:32.3760000" , "Fri, 14 Feb 2014 09:15:32 GMT" , "2014-02-14T09:15:32" , "9:15" , "9:15:32" , "2014-02-14 09:15:32Z" , "??????????? 14 ?????????? 2014 9:15:32" , "?????????? 2557"}; //Act String[] actualResults = new String[15]; for (int i = 0; i < formats.Length; i++) { actualResults[i] = controller.FormatAsSpecified(theDate, theCulture, formats[i]); } //Assert CollectionAssert.AreEqual(expectedResults, actualResults); } I get an error in the test method at 'controller.FormatAsSpecified(theDate, theCulture, formats[i]);' that says "Argument 3, cannot convert from 'string' to 'string[]'" What am I doing wrong?

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• returning opengl display callback in D

  - by Max

  I've written a simple hello world opengl program in D, using the converted gl headers here. My code so far: import std.string; import c.gl.glut; Display_callback display() { return Display_callback // line 7 { return; // just display a blank window }; } // line 10 void main(string[] args) { glutInit(args.length, args); glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE); glutInitWindowSize(800,600); glutCreateWindow("Hello World"); glutDisplayFunc(display); glutMainLoop(); } My problem is with the display() function. glutDisplayFunc() expects a function that returns a Display_callback, which is typedef'd as typedef GLvoid function() Display_callback;. When I try to compile, dmd says line 7: found '{' when expecting ';' following return statement line 10: unrecognized declaration How do I properly return the Display_callback here? Also, how do I change D strings and string literals into char*? My calls to glutInit and glutCreateWindow don't like the D strings they're getting. Thanks for your help.

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• Java reflection appropriateness

  - by jsn

  This may be a fairly subjective question, but maybe not. My application contains a bunch of forms that are displayed to the user at different times. Each form is a class of its own. Typically the user clicks a button, which launches a new form. I have a convenience function that builds these buttons, you call it like this: buildButton( "button text", new SelectionAdapter() { @Override public void widgetSelected( SelectionEvent e ) { showForm( new TasksForm( args... ) ); } } ); I do this dozens of times, and it's really cumbersome having to make a SelectionAdapter every time. Really all I need for the button to know is what class to instantiate when it's clicked and what arguments to give the constructor, so I built a function that I call like this instead: buildButton( "button text", TasksForm.class, args... ); Where args is an arbitrary list of objects that you could use to instantiate TasksForm normally. It uses reflection to get a constructor from the class, match the argument list, and build an instance when it needs to. Most of the time I don't have to pass any arguments to the constructor at all. The downside is obviously that if I'm passing a bad set of arguments, it can't detect that at compilation time, so if it fails, a dialog is displayed at runtime. But it won't normally fail, and it'll be easy to debug if it does. I think this is much cleaner because I come from languages where the use of function and class literals is pretty common. But if you're a normal Java programmer, would seeing this freak you out, or would you appreciate not having to scan a zillion SelectionAdapters?

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• Is there a definitive reference document for Ruby syntax?

  - by JSW

  I'm searching for a definitive document on Ruby syntax. I know about the definitive documents for the core API and standard library, but what about the syntax itself? For instance, such a document should cover: reserved words, string literals syntax, naming rules for variables/classes/modules, all the conditional statements and their permutations, and so forth. I know there are many books and tutorials, yes, but every one of them is essentially a tutorial, each one having a range of different depth and focus. They will all, by necessity of brevity and narrative flow, omit certain details of the language that the author deems insignificant. For instance, did you know that you can use a case statement without an initial case value, and it will then execute the first true when clause? Any given Ruby book or tutorial may or may not cover that particular lesser-known functionality of the case syntax. It's not discussed in the section in "Programming Ruby" about case statements. But that is just one small example. So far the best documentation I've found is the rubyspec project, which appears to be an attempt to write a complete test suite for the language. That's not bad, but it's a bit hard to use from a practical standpoint as a developer working on my own projects. Am I just missing something or is there really no definitive readable document defining the whole of Ruby syntax?

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• Comparing strings that contain formatting in C#

  - by Finglas

  I'm working on a function that given some settings - such as line spacing, the output (in string form) is modified. In order to test such scenarios, I'm using string literals, as shown below for the expected result. The method, using a string builder, (AppendLine) generates the said output. One issue I have run into is that of comparing such strings. In the example below, both are equal in terms of what they represent. The result is the area which I care about, however when comparing two strings, one literal, one not, equality naturally fails. This is because one of the strings emits line spacing, while the other only demonstrates the formatting it contains. What would be the best way of solving this equality problem? I do care about formatting such as new lines from the result of the method, this is crucially important. Code: string expected = @"Test\n\n\nEnd Test."; string result = "Test\n\n\nEnd Test"; Console.WriteLine(expected); Console.WriteLine(result); Output: Test\n\n\nEnd Test. Test End Test

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• Tips for submitting a library to Boost?

  - by AraK

  Hi everyone, Summer is coming, and a group of friends and I are getting ready for it :) We decided to build a compile-time Arbitrary precision Unsigned Integers. We would like to provide a set of integers algorithms(functions) with the library. We have seen a number of requests for such a library(SoC2010, C++0x Standard Library wishlist). Also, a regular run-time bigint is requested usually with that, but we don't want to go into the hassle of memory management. The idea came to me from a library called TTMath, unfortunately this library works only on specific platforms because Assembly was used extensively in the library. We would like to write a standard library, depending on the C++ standard library and Boost. Also, we would like to use the available C++0x facilities in current compilers like user-defined literals and others. This would technically make the library non-standard for a while, but we think that it is a matter of time the new standards will be official. Your hints on the whole process including design, implementation, documentation, maintainable of the library are more than welcom. We are a group of students and fresh graduates who are looking for something interesting in the summer, but we see that Boost is full of gurus and we don't want to forget something too obvious. We are communicating on-line, so there is no shared white-boards :( Thanks,

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• Identical files from different servers. Why might IE 8 display them differently?

  - by jasongetsdown

  I'm working on a site that will go on my company's intranet. I developed it locally on my computer, checking it in different browsers and on colleague's computers, and when it was done I handed it off to IT. They put identical copies on a staging server, and on the production server. This is a site built only with html, javascript, and css. No server side scripting. It also uses a DWF viewer plugin from Autodesk. It is a single standalone page (not part of a CMS) that allows users to load drawings into the viewer and then click to see info from a database of space info saved in a series of js arrays (the space DB software spits out a js file with all the info listed in array literals, creating a crap ton of global variables - ugh, but I digress). When I followed their links (using IE 8) the version on the staging server looked as expected, but the layout is hosed on the version from the production server. Specifically, it seems like a div that is supposed to flow to the right of a div that is float: left is displaying below the floated div at full width, as though it was clear: left (which it is not). It also has the wrong height. I downloaded the files from each and they are identical to my local version. Frustrated, I cleared my browser's cache, restarted my computer, checked it on a colleague's computer who also has IE 8. All the same issue. Staging server good. Production server bad. Finally I uninstalled IE 8 and looked at it in IE 6. Both versions looked fine. So, to recap. Two different servers. No server side scripting. Identical files. One browser agrees they are identical, the other does not. What could cause this?

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• RegEx: difference between "(?:...) and normal parentheses

  - by N0thing

  >>> re.findall(r"(?:do|re|mi)+", "mimi") ['mimi'] >>> re.findall(r"(do|re|mi)+", "mimi") ['mi'] According to my understanding of the definitions, it should produce the same answer. The only difference between (...) and (?:...) should be whether or not we can use back-references later. Am I missing something? (...) Matches whatever regular expression is inside the parentheses, and indicates the start and end of a group; the contents of a group can be retrieved after a match has been performed, and can be matched later in the string with the \number special sequence, described below. To match the literals '(' or ')', use ( or ), or enclose them inside a character class: [(] [)]. (?:...) A non-capturing version of regular parentheses. Matches whatever regular expression is inside the parentheses, but the substring matched by the group cannot be retrieved after performing a match or referenced later in the pattern.

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• Creating serializeable unique compile-time identifiers for arbitrary UDT's.

  - by Endiannes

  I would like a generic way to create unique compile-time identifiers for any C++ user defined types. for example: unique_id<my_type>::value == 0 // true unique_id<other_type>::value == 1 // true I've managed to implement something like this using preprocessor meta programming, the problem is, serialization is not consistent. For instance if the class template unique_id is instantiated with other_type first, then any serialization in previous revisions of my program will be invalidated. I've searched for solutions to this problem, and found several ways to implement this with non-consistent serialization if the unique values are compile-time constants. If RTTI or similar methods, like boost::sp_typeinfo are used, then the unique values are obviously not compile-time constants and extra overhead is present. An ad-hoc solution to this problem would be, instantiating all of the unique_id's in a separate header in the correct order, but this causes additional maintenance and boilerplate code, which is not different than using an enum unique_id{my_type, other_type};. A good solution to this problem would be using user-defined literals, unfortunately, as far as I know, no compiler supports them at this moment. The syntax would be 'my_type'_id; 'other_type'_id; with udl's. I'm hoping somebody knows a trick that allows implementing serialize-able unique identifiers in C++ with the current standard (C++03/C++0x), I would be happy if it works with the latest stable MSVC and GNU-G++ compilers, although I expect if there is a solution, it's not portable.

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• What new Unicode functions are there in C++0x?

  - by luiscubal

  It has been mentioned in several sources that C++0x will include better language-level support for Unicode(including types and literals). If the language is going to add these new features, it's only natural to assume that the standard library will as well. However, I am currently unable to find any references to the new standard library. I expected to find out the answer for these answers: Does the new library provide standard methods to convert UTF-8 to UTF-16, etc.? Does the new library allowing writing UTF-8 to files, to the console (or from files, from the console). If so, can we use cout or will we need something else? Does the new library include "basic" functionality such as: discovering the byte count and length of a UTF-8 string, converting to upper-case/lower-case(does this consider the influence of locales?) Finally, are any of these functions are available in any popular compilers such as GCC or Visual Studio? I have tried to look for information, but I can't seem to find anything? I am actually starting to think that maybe these things aren't even decided yet(I am aware that C++0x is a work in progress).

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• Need help debugging a huge chunk of JSON data...

  - by meder

  I have a huge chunk, so large that I can't manually edit the file and need to read it in and do regex operations to see what's wrong. Basically - my server is PHP 5.1.6 and I can't update it. This features an older json_decode which is less featured than the 5.2/5.3 versions. json_decode returns NULL and json_last_error is being invoked but the function doesn't exist except in PHP 5.3 so I'm manually trying to see what's wrong. $regex = '#[^0-9"$a-zA-Z{:}().]#'; $json = preg_replace( $regex, '', $json ); $tree = json_decode ( $json, true ); var_dump($tree); // NULL A snippet of the JSON.. somewhere in the middle {"109":0,"103":1,"102":59,"101":70,"100":4299,"94":0,"50":51,"46":0,"45":0,"44":0,"43":0,"42":0,"23":0,"22":0,"18":0,"17":1,"16":1,"13":160,"8":4298}},"2":{"d":{"109":0,"103":92,"102":54,"101":53,"100":4301,"94":0,"50":4278,"49":328,"46":1,"45":0,"44":1,"43":0,"42":0,"26":0,"23":0,"22":0,"18":0,"17":1,"16":1,"8":4300},"m":{"94":1,"100":1,"26":1,"50":1,"8":1,"49":1,"18":1,"43":1,"42":1,"109":1},"c":{"\/":{"d":{"109":0,"100":4301,"94":0,"50":4278,"49":328,"43":0,"42":0,"26":0,"18":0,"8":4300}},"G":{"d":{"109":1,"100":4303,"94":1,"68":17,"50":64,"49":53,"43":1,"42":1,"34":0,"18":1,"13":2216,"11":0,"8":4302}}}},"3": The }}}} is suspicious but this probably just closes 4 nested object literals. Would appreciate any insight.

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• Perl need the right grep operator to match value of variable

  - by iaintunderstand

  I want to see if I have repeated items in my array, there are over 16.000 so will automate it There may be other ways but I started with this and, well, would like to finish it unless there is a straightforward command. What I am doing is shifting and pushing from one array into another and this way, check the destination array to see if it is "in array" (like there is such a command in PHP). So, I got this sub routine and it works with literals, but it doesn't with variables. It is because of the 'eq' or whatever I should need. The 'sourcefile' will contain one or more of the words of the destination array. my @destination = ('hi', 'bye'); sub in_array { my ($destination,$search_for) = @_; return grep {$search_for eq $_} @$destination; } for($i = 0; $i <=100; $i ++) { $elemento = shift @sourcefile; if(in_array(\@destination, $elemento)) { print "it is"; } else { print "it aint there"; } } Well, if instead of including the $elemento in there I put a 'hi' it does work and also I have printed the value of $elemento which is also 'hi', but when I put the variable, it does not work, and that is because of the 'eq', but I don't know what else to put. If I put == it complains that 'hi' is not a numeric value.

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• C#/.NET Little Wonders &ndash; Cross Calling Constructors

  - by James Michael Hare

  Just a small post today, it’s the final iteration before our release and things are crazy here!  This is another little tidbit that I love using, and it should be fairly common knowledge, yet I’ve noticed many times that less experienced developers tend to have redundant constructor code when they overload their constructors. The Problem – repetitive code is less maintainable Let’s say you were designing a messaging system, and so you want to create a class to represent the properties for a Receiver, so perhaps you design a ReceiverProperties class to represent this collection of properties. Perhaps, you decide to make ReceiverProperties immutable, and so you have several constructors that you can use for alternative construction: 1: // Constructs a set of receiver properties. 2: public ReceiverProperties(ReceiverType receiverType, string source, bool isDurable, bool isBuffered) 3: { 4: ReceiverType = receiverType; 5: Source = source; 6: IsDurable = isDurable; 7: IsBuffered = isBuffered; 8: } 9: 10: // Constructs a set of receiver properties with buffering on by default. 11: public ReceiverProperties(ReceiverType receiverType, string source, bool isDurable) 12: { 13: ReceiverType = receiverType; 14: Source = source; 15: IsDurable = isDurable; 16: IsBuffered = true; 17: } 18:  19: // Constructs a set of receiver properties with buffering on and durability off. 20: public ReceiverProperties(ReceiverType receiverType, string source) 21: { 22: ReceiverType = receiverType; 23: Source = source; 24: IsDurable = false; 25: IsBuffered = true; 26: } Note: keep in mind this is just a simple example for illustration, and in same cases default parameters can also help clean this up, but they have issues of their own. While strictly speaking, there is nothing wrong with this code, logically, it suffers from maintainability flaws.  Consider what happens if you add a new property to the class?  You have to remember to guarantee that it is set appropriately in every constructor call. This can cause subtle bugs and becomes even uglier when the constructors do more complex logic, error handling, or there are numerous potential overloads (especially if you can’t easily see them all on one screen’s height). The Solution – cross-calling constructors I’d wager nearly everyone knows how to call your base class’s constructor, but you can also cross-call to one of the constructors in the same class by using the this keyword in the same way you use base to call a base constructor. 1: // Constructs a set of receiver properties. 2: public ReceiverProperties(ReceiverType receiverType, string source, bool isDurable, bool isBuffered) 3: { 4: ReceiverType = receiverType; 5: Source = source; 6: IsDurable = isDurable; 7: IsBuffered = isBuffered; 8: } 9: 10: // Constructs a set of receiver properties with buffering on by default. 11: public ReceiverProperties(ReceiverType receiverType, string source, bool isDurable) 12: : this(receiverType, source, isDurable, true) 13: { 14: } 15:  16: // Constructs a set of receiver properties with buffering on and durability off. 17: public ReceiverProperties(ReceiverType receiverType, string source) 18: : this(receiverType, source, false, true) 19: { 20: } Notice, there is much less code.  In addition, the code you have has no repetitive logic.  You can define the main constructor that takes all arguments, and the remaining constructors with defaults simply cross-call the main constructor, passing in the defaults. Yes, in some cases default parameters can ease some of this for you, but default parameters only work for compile-time constants (null, string and number literals).  For example, if you were creating a TradingDataAdapter that relied on an implementation of ITradingDao which is the data access object to retreive records from the database, you might want two constructors: one that takes an ITradingDao reference, and a default constructor which constructs a specific ITradingDao for ease of use: 1: public TradingDataAdapter(ITradingDao dao) 2: { 3: _tradingDao = dao; 4:  5: // other constructor logic 6: } 7:  8: public TradingDataAdapter() 9: { 10: _tradingDao = new SqlTradingDao(); 11:  12: // same constructor logic as above 13: }   As you can see, this isn’t something we can solve with a default parameter, but we could with cross-calling constructors: 1: public TradingDataAdapter(ITradingDao dao) 2: { 3: _tradingDao = dao; 4:  5: // other constructor logic 6: } 7:  8: public TradingDataAdapter() 9: : this(new SqlTradingDao()) 10: { 11: }   So in cases like this where you have constructors with non compiler-time constant defaults, default parameters can’t help you and cross-calling constructors is one of your best options. Summary When you have just one constructor doing the job of initializing the class, you can consolidate all your logic and error-handling in one place, thus ensuring that your behavior will be consistent across the constructor calls. This makes the code more maintainable and even easier to read.  There will be some cases where cross-calling constructors may be sub-optimal or not possible (if, for example, the overloaded constructors take completely different types and are not just “defaulting” behaviors). You can also use default parameters, of course, but default parameter behavior in a class hierarchy can be problematic (default values are not inherited and in fact can differ) so sometimes multiple constructors are actually preferable. Regardless of why you may need to have multiple constructors, consider cross-calling where you can to reduce redundant logic and clean up the code.   Technorati Tags: C#,.NET,Little Wonders

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• Efficiency of Java "Double Brace Initialization"?

  - by Jim Ferrans

  In Hidden Features of Java the top answer mentions Double Brace Initialization, with a very enticing syntax: Set<String> flavors = new HashSet<String>() {{ add("vanilla"); add("strawberry"); add("chocolate"); add("butter pecan"); }}; This idiom creates an anonymous inner class with just an instance initializer in it, which "can use any [...] methods in the containing scope". Main question: Is this as inefficient as it sounds? Should its use be limited to one-off initializations? (And of course showing off!) Second question: The new HashSet must be the "this" used in the instance initializer ... can anyone shed light on the mechanism? Third question: Is this idiom too obscure to use in production code? Summary: Very, very nice answers, thanks everyone. On question (3), people felt the syntax should be clear (though I'd recommend an occasional comment, especially if your code will pass on to developers who may not be familiar with it). On question (1), The generated code should run quickly. The extra .class files do cause jar file clutter, and slow program startup slightly (thanks to coobird for measuring that). Thilo pointed out that garbage collection can be affected, and the memory cost for the extra loaded classes may be a factor in some cases. Question (2) turned out to be most interesting to me. If I understand the answers, what's happening in DBI is that the anonymous inner class extends the class of the object being constructed by the new operator, and hence has a "this" value referencing the instance being constructed. Very neat. Overall, DBI strikes me as something of an intellectual curiousity. Coobird and others point out you can achieve the same effect with Arrays.asList, varargs methods, Google Collections, and the proposed Java 7 Collection literals. Newer JVM languages like Scala, JRuby, and Groovy also offer concise notations for list construction, and interoperate well with Java. Given that DBI clutters up the classpath, slows down class loading a bit, and makes the code a tad more obscure, I'd probably shy away from it. However, I plan to spring this on a friend who's just gotten his SCJP and loves good natured jousts about Java semantics! ;-) Thanks everyone!

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