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• Parenthesis operator in C. What is the effect in the following code

  - by Andre

  Hi everyone, I was playing with a macro to enable/disable traces when I came out with the following code when the macro is disabled: int main { ("Hello world"); } This code is valid and I got the desired effect (nothing happens when the macro is disabled) but I couldn't figure out what exactly is happening. Is the compiler seeing the parenthesis as a "nameless" method declaration? To make it clearer the code is : #ifdef TRACE #define trace printf("%s %d -> ",__FILE__, __LINE__);printf else #define trace #endif int main { trace("Hello world"); } Thanks in advance.

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• Compile-time trigonometry in C

  - by lhahne

  I currently have code that looks like while (very_long_loop) { ... y1 = getSomeValue(); ... x1 = y1*cos(PI/2); x2 = y2*cos(SOME_CONSTANT); ... outputValues(x1, x2, ...); } the obvious optimization would be to compute the cosines ahead-of-time. I could do this by filling an array with the values but I was wondering would it be possible to make the compiler compute these at compile-time?

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• Why do Java source files go into a directory structure?

  - by bdhar

  Suppose that I am creating a Java project with the following classes com.bharani.ClassOne com.bharani.ClassTwo com.bharani.helper.HelperOne com.bharani.helper.support.HelperTwo with files put immediately under the folder 'src' src/ClassOne.java src/ClassTwo.java src/HelperOne.java src/HelperTwo.java and compile them using the command $ javac src/*.java -d classes (assuming that classes directory exists) The compiler compiles these files and put the class files in appropriate sub-directories inside the 'classes' directory like this classes/com/bharani/ClassOne.class classes/com/bharani/ClassTwo.class classes/com/bharani/helper/HelperOne.class classes/com/bharani/helper/support/HelperTwo.class Because the spec mandates that the classes should go inside appropriate directory structure. Fine. My question is this: When I use an IDE such as Eclipse or NetBeans, they create the directory structure for the source code directory ('src' directory here) also. Why is that? Is it mandatory? Or, is it just a convention? Thanks.

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• Standard (cross-platform) way for bit manipulation

  - by Kiril Kirov

  As are are different binary representation of the numbers (for example, take big/little endian), is this cross-platform: some_unsigned_type variable = some_number; // set n-th bit, starting from 1, // right-to-left (least significant-to most significant) variable |= ( 1 << ( n - 1 ) ); // clear the same bit: variable &= ~( 1 << ( n - 1 ) ); In other words, does the compiler always take care of the different binary representation of the unsigned numbers, or it's platform-specific? And what if variable is signed integral type (for example, int) and its value is zero positive negative? What does the Standard say about this? P.S. And, yes, I'm interesting in both - C and C++, please don't tell me they are different languages, because I know this :) I can paste real example, if needed, but the post will become too long

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• Eclipse RCP standalone export problem with Groovy scripts

  - by geejay

  I am trying to export a standalone RCP app using Eclipse 3.5.2. The app has a main pure Java plug-in, and a Java / Groovy plug-in that is used by the main plug-in. When I export the main RCP plug-in using the "Export Wizard", I get compiler errors saying that the Groovy classes cannot be found, e.g ERROR in C:\mysrc\src\ch\calcs\providers\CalcProvider.java (at line 8) import ch.calcs.ArgSet; This plug-in works fine when run from within Eclipse. Any ideas?

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• Netbeans C++ not finding standard libraries (Macintosh)

  - by Grue

  Hello everyone! I am trying to use Netbeans 6.7 (on a Mac) to create C++ applications. I started out with the standard "Hello World," just to test if everything was working correctly. First try std and could not be found. So I tried reinstalling the developer tools on my Mac OS X disk. After that Netbeans updated its c++ compiler info, but still cannot find std or . Odder than this XCode seems to be working with C++ perfectly fine. Any help fixing this would be greatly appreciated.

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• Does Msbuild recognise any build configurations other than DEBUG|RELEASE

  - by Dean

  I created a configuration named Test via Visual Studio which currently just takes all of DEBUG settings, however I employ compiler conditions to determine some specific actions if the build happens to be TEST|DEBUG|RELEASE. However how can I get my MSBUILD script to detect the TEST configuration?? Currently I build <MSBuild Projects="@(SolutionsToBuild)" Properties="Configuration=$(Configuration);OutDir=$(BuildDir)\Builds\" /> Where @(SolutionsToBuild) is a my solution. In the Common MsBuild Project Properties it states that $(Configuration) is a common property but it always appears blank? Does this mean that it never gets set but is simply reserved for my use or that it can ONLY detect DEBUG|RELEASE. If so what is the point in allowing the creation of different build configurations?

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• saving a records containing a member of type string to a file (Delphi, Windows)

  - by wonderer

  I have a record that looks similar to: type TNote = record Title : string; Note : string; Index : integer; end; Simple. The reason I chose to set the variables as string (as opposed to an array of chars) is that I have no idea how long those strings are going to be. They can be 1 char long, 200 or 2000. Of course when I try to save the record to a type file (file of...) the compiler complains that I have to give a size to string. Is there a way to overcome this? or a way to save those records to an untyped file and still maintain a sort of searchable way? Please do not point me to possible solutions, if you know the solution please post code. Thank you

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• Explicit initialization of struct/class members

  - by Zephon

  struct some_struct{ int a; }; some_struct n = {}; n.a will be 0 after this; I know this braces form of initialization is inherited from C and is supported for compatibility with C programs, but this only compiles with C++, not with the C compiler. I'm using Visual C++ 2005. In C this type of initialization struct some_struct n = {0}; is correct and will zero-initialize all members of a structure. Is the empty pair of braces form of initialization standard? I first saw this form of initialization in a WinAPI tutorial from msdn.

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• Stop CDATA tags from being output-escaped when writing to XML in C#

  - by Smallgods

  We're creating a system outputting some data to an XML schema. Some of the fields in this schema need their formatting preserved, as it will be parsed by the end system into potentially a Word doc layout. To do this we're using <![CDATA[Some formatted text]]> tags inside of the App.Config file, then putting that into an appropriate property field in a xsd.exe generated class from our schema. Ideally the formatting wouldn't be out problem, but unfortunately thats just how the system is going. The App.Config section looks as follows: <header> <![CDATA[Some sample formatted data]]> </header> The data assignment looks as follows: HeaderSection header = ConfigurationManager.GetSection("header") as HeaderSection; report.header = "<[CDATA[" + header.Header + "]]>"; Finally, the Xml output is handled as follows: xs = new XmlSerializer(typeof(report)); fs = new FileStream (reportLocation, FileMode.Create); xs.Serialize(fs, report); fs.Flush(); fs.Close(); This should in theory produce in the final Xml a section that has information with CDATA tags around it. However, the angled brackets are being converted into &lt; and &gt; I've looked at ways of disabling Outout Escaping, but so far can only find references to XSLT sheets. I've also tried @"<[CDATA[" with the strings, but again no luck. Any help would be appreciated!

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• Apache console accesses network drives, service does not?

  - by danspants

  I have an apache 2.2 server running Django. We have a network drive T: which we need constant access to within our Django app. When running Apache as a service, we cannot access this drive, as far as any django code is concerned the drive does not exist. If I add... <Directory "t:/"> Options Indexes FollowSymLinks MultiViews AllowOverride None Order allow,deny allow from all </Directory> to the httpd.conf file the service no longer runs, but I can start apache as a console and it works fine, Django can find the network drive and all is well. Why is there a difference between the console and the service? Should there be a difference? I have the service using my own log on so in theory it should have the same access as I do. I'm keen to keep it running as a service as it's far less obtrusive when I'm working on the server (unless there's a way to hide the console?). Any help would be most appreciated.

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• Has anyone been successful at a assembler based led blinker for an xcore?

  - by dwelch

  I am liking the http://www.xmos.com chips but want to get a lower level understanding of what is going on. Basically assembler. I am trying to sort out something as simple as an led blinker, set the led, count to N clear the led, count to N, loop forever. Sure I can disassemble a 10 line XC program, but if you have tried that you will see there is a lot of bloat in there that is in every program, what bits are to support the compiler output and what bits are actually setting up the gpio?

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• Void in main and keeping Dos program from dying

  - by TimothyTech

  Alright, so im using bloodshed complier, first thing i should note is im using a 2001 edition C++ for the aboslute beginner, was there any changes to C++ since 2001 that would effect the validity of this book? i ask because i know php has php5 and now php6 but i havent seen any C++3. now for the reason i asked that, in this code it uses, void main (void) why would i want an arguement to be void? what does this do. But when i run the " void main (void) in my compiler it says that main must have a "int" before it. so i cant have "void" main (void); also, once the code runs through, as long as there isnt a "cin" the program closes. is this normal behavior, is there a better way to stop this besides making a cin at the end of my program.

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• error handling strategies in C?

  - by Leo

  Given the code below: typedef struct {int a;} test_t; arbitrary_t test_dosomething(test_t* test) { if (test == NULL) { //options: //1. print an error and let it crash //e.g. fprintf(stderr, "null ref at %s:%u", __FILE__, __LINE__); //2. stop the world //e.g. exit(1); //3. return (i.e. function does nothing) //4. attempt to re-init test } printf("%d", test->a); //do something w/ test } I want to get a compiler error if test is ever NULL, but I guess that's not possible in C. Since I need to do null checking at runtime, what option is the most proper way to handle it?

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• Custom class object in Initialization list

  - by Michael

  I have a class Bar: class Bar { public: Bar(void); ~Bar(void); }; And a class Foo that gets a reference to Bar object as a constructor parameter and needs to save it in a private member bar_ : class Foo { private: Bar& bar_; public: Foo(Bar& bar) : bar_(bar) {} ~Foo(void) {} }; This doesn't compile : overloaded member function not found in 'Parser' missing type specifier - int assumed. Note: C++ does not support default-int Now i suspect couple of things that i need to assure, the second error is for Bar& bar_; declaration in Foo. Do i need to use an explicit constructor when declaring bar_ ? I am interested in learning how the compiler works regarding this matter, so a detailed explanation would be highly appreciated. Thanks.

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• Does C# compile code inside an if(false) block?

  - by aximili

  I am just wondering if these code blocks gets compiled into .dll I don't think this one gets compiled at all #if SOMETHING_UNDEFINED // some code - this is ignored by the compiler #endif Now what about these? 1. if(false) { // some code - is this compiled? } 2. const bool F = false; if(F) { // some code - is this compiled? } 3. bool F = false; if(F) { // some code - is this compiled? }

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• Coping with weak typing

  - by John Leonard

  I'm a front end Flex developer peeking over the wall at html. One of the things I have a hard time with is weak typing in Javascript. I know many developers say they prefer it. How do I stop worrying and learn to love the weak typing? Are there best practices for variable naming that help make var types human readable? Another thing I have trouble with is getting by without my trusted compiler errors and warnings. I'm getting along with firebug. Is there anything else I should have in my toolkit?

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• "Inherited" types in C++

  - by Ken Moynihan

  The following code does not compile. I get an error message: error C2039: 'Asub' : is not a member of 'C' Can someone help me to understand this? Tried VS2008 & 2010 compiler. template <class T> class B { typedef int Asub; public: void DoSomething(typename T::Asub it) { } }; class C : public B<C> { public: typedef int Asub; }; class A { public: typedef int Asub; }; int _tmain(int argc, _TCHAR* argv[]) { C theThing; theThing.DoSomething(C::Asub()); return 0; }

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• How to run an exe using c prog

  - by Ujjwal

  Hi All, I am new to this forum. I am in need of a program in C that runs an exe file in Windows. While googling I found the code below : 1. Code: #include<stdlib.h> #include<stdio.h> int main() { (void)system("C:\\Windows\\notepad.exe"); return 0; } The above code compiles successfully in Borland Turbo C. But it fails to run Notepad. 2 Code: #include<stdlib.h> #include<stdio.h> void main() { int result ; result=system("C:\\Windows\\notepad.exe"); printf("%d",result); } The above code on running gives -1 as output. Why am I getting -1. My OS Windows XP Borland Turbo C Compiler Please help.

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• xml to xsd to c# class - C# 3.0, .net 3.5

  - by uno

  Following this articlelink text one of the comments from 'zanoni' said he did it this way Using .NET 3.5: [XmlRoot] public class EmailConfiguration { [XmlElement] public string DataBoxID { get; set; } [XmlElement] public DefaultSendToAddressCollectionClass DefaultSendToAddressCollection { get; set; } } public class DefaultSendToAddressCollectionClass { [XmlElement] public string[] EmailAddress { get; set; } } How would I get my class to be as what he described? I ran the xsd tool and it is in the fashion as what shane posted in the above link [System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "2.0.50727.3038")] [System.SerializableAttribute()] [System.Diagnostics.DebuggerStepThroughAttribute()] [System.ComponentModel.DesignerCategoryAttribute("code")] [System.Xml.Serialization.XmlTypeAttribute(AnonymousType=true)] [System.Xml.Serialization.XmlRootAttribute(Namespace="", IsNullable=false)] public partial class EmailConfiguration : object, System.ComponentModel.INotifyPropertyChanged { private string dataBoxIDField; private EmailConfigurationDefaultSendToAddressCollection[] defaultSendToAddressCollectionField; /// <remarks/> [System.Xml.Serialization.XmlElementAttribute(Form=System.Xml.Schema.XmlSchemaForm.Unqualified)] public string DataBoxID { get { return this.dataBoxIDField; } set { this.dataBoxIDField = value; this.RaisePropertyChanged("DataBoxID"); } }

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• C++: Cannot convert from foo& to foo*

  - by Rosarch

  I have a method: odp(foo& bar); I'm trying to call it: foo baz; odp(&baz); I get a compiler error: error C2664: "odp" cannot convert parameter 1 from 'foo *' to 'foo &' What am I doing wrong? Aren't I passing in a reference to baz? UPDATE: Perhaps I have a misconception about the relationship between pointers and references. I thought that they were the same, except references couldn't be null. Is that incorrect?

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• Jquery number of clicks record

  - by Maxime

  Hi, I am working on this page where I'm using a Jquery Mp3 Player (Jplayer) with its playlist. What I want to do is very simple in theory: I want to record the number of clicks for every playlist element. When someone enters the page, his number of clicks are at 0 for every element. The visitor can click a few times on element #1, then go to element #2 (which will be at 0), then come back to element #1 and the number of clicks must be saved. We don't need to save it for next visits. Jplayer has this function that loads each time a new playlist element is being loaded: function playListChange( index ) In which every element has its own ID dynamically updated: myPlayList[index].song_id Here's my code: function playListChange( index ) { var id = myPlayList[index].song_id; if(!o) { var o = {}; } if(!o[id]) { o[id] = 0; } alert(o[id]); … $("#mydiv").click { o[id] = o[id]+1; } … But o[id] is reset every time and the alert always show 0. Why? Thanks for any reply.

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• Visual Studio 2008 awful performance

  - by Nima

  Hi, I have ported a piece of C++ code, that works out of core, from Linux(Ubuntu) to Windows(Vista) and I realized that it works about 50times slower on VS2008! I removed all the out of core parts and now I just have a piece of code that has nothing to do with the hard disk. I set compiler parameters to O2 in Project Properties but still get about 10times slower than g++ in linux! Does anybody have an idea why it is this much slower under VS? I really appreciate any kind of hint! Thanks,

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• How to free memory in try-catch blocks?

  - by Kra

  Hi, I have a simple question hopefully - how does one free memory which was allocated in the try block when the exception occurs? Consider the following code: try { char *heap = new char [50]; //let exception occur here delete[] heap; } catch (...) { cout << "Error, leaving function now"; //delete[] heap; doesn't work of course, heap is unknown to compiler return 1; } How can I free memory after the heap was allocated and exception occurred before calling delete[] heap? Is there a rule not to allocate memory on heap in these try .. catch blocks? Thanks

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• Create Generic Class Instance from Static Method in a Derived Class

  - by user343547

  I have a class in C# with a template and static method similar to class BClass<T> { public static BClass<T> Create() { return new BClass<T>(); } } From this I derive a class and specify a template parameter to the base class class DClass : BClass<int> { } A problem occurs when I try to use the static method to create an instance of D class Program { static void Main(string[] args) { DClass d = DClass.Create(); } } Gives a compiler error "Cannot implicitly convert type 'Test.BClass<int ' to 'Test.DClass'." Adding the below cast leads to a runtime casting exception. DClass d = (DClass)DClass.Create(); Is there any succint way to allow the static method to create instances of the derived class? Ideally I would like the equivalent of a c++ typedef and I don't want the below syntax (which does work). BClass<int> d = DClass.Create();

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