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  • Function return type style

    - by JB
    I'm learning c++0x, at least the parts supported by the Visual C++ Express 2010 Beta. This is a question about style rather than how it works. Perhaps it's too early for style and good practice to have evolved yet for a standard that isn't even released yet... In c++0x you can define the return type of a method using - type at the end of the function instead of putting the type at the start. I believe this change in syntax is required due to lambdas and some use cases of the new decltype keyword, but you can use it anywhere as far as I know. // Old style int add1(int a, int b) { return a + b; } // New style return type auto add2(int a, int b) -> int { return a + b; } My question really then, is given that some functions will need to be defined in the new way is it considered good style to define all functions in this way for consistency? Or should I stick to only using it when necessary?

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  • Finding greatest product of two lists, but keep getting #unspecific

    - by user1787030
    (define (greatest-product lst1 lst2) (define (helper lst addtimes total toacc) (cond ((null? lst) '()) ((= (countatoms lst) 1) (display total)) ((= addtimes (cadr lst)) (helper (cdr lst) 1 total total)) (else (helper lst (+ 1 addtimes) (+ toacc total) toacc)))) (cond ((> (helper lst1 0 0 (car lst1)) (helper lst2 0 0 (car lst2))) (helper lst1 0 0 (car lst1))) ((< (helper lst1 0 0 (car lst1)) (helper lst2 0 0 (car lst2))) (helper lst2 0 0 (car lst2))) ((= (helper lst1 0 0 (car lst1)) (helper lst2 0 0 (car lst2))) (display 'equal)))) Scheme keeps returning back that it cannot perform the procedure with #unspecific Im running it with (display (greatest-product '(1 2 3) '(4 5 6))) (display (greatest-product '(1 2 3) '(1 2 3))) (display (greatest-product '(1 2 3) '())) what is wrong with it? the problem seems to be occurring

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  • Masking a bit in C returning unexpected result

    - by Eamorr
    0x7F000000 is 0111 1111 0000 0000 0000 0000 0000 0000 in 32 bit binary. 0x01000058 is 0000 0001 0000 0000 0000 0000 0101 1000. When I AND the two numbers together I expect 0000 0001 0000 0000 0000 0000 0000 0000, but for some reason I get 0. Here is my code: #define MASK_binop 0x80000000 #define MASK_operation 0x7F000000 int instruction=atoi(line); if((MASK_binop & instruction)>0) printf("binop\n"); else if((MASK_operation & instruction)>0) printf("operation\n"); Each of the above comparisons keeps returning zero. Is it something to do with 32/64 bits? I'm using 64-bit compiler.

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  • SEO Language information

    - by Kevin
    I was wondering if defining your language in HTML is better for search enigines. For example, I've got a French site, then i've got three options: 1.) have faith that google can say my site is french 2.) define language in the HTML tag <html xmlns="http://www.w3.org/1999/xhtml" dir="ltr" lang="fr"> 3.) define language in a meta tag <meta http-equiv="content-language" content="FR-fr" /> Which option you believe is best? Or which combination of options?

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  • Is there a way to know if std::chrono::monotonic_clock is defined?

    - by Vicente Botet Escriba
    C++0X N3092 states that monotonic_clock is optional. 20.10.5.2 Class monotonic_clock [time.clock.monotonic] 1 Objects of class monotonic_clock represent clocks for which values of time_point never decrease as physical time advances. monotonic_clock may be a synonym for system_clock if system_clock::is_monotonic is true. ** 2 The class monotonic_clock is conditionally supported.** Is there a way using SFINAE or another technique to define a traits class that states if monotonic_clock is defined? struct is_monotonic_clock_defined; If yes, how? If not, shouldn't the standard define macro that gives this information at preprocessing time?

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  • How do I change the list using mutable lists in Racket or Scheme?

    - by exOne
    I need your help Can anyone help me? first question This procedure should modify each element which’s index in the list is even. The value of the element should be equal to the new-element. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-indices number-list 10) The new list: 1 10 8 10 43 10 78 second question This problem is the extended version of Question 1. (modify-even-odd-indices my-list new-element modification-type) This procedure should modify each element according to the modification-type. The modification-type can be even or odd. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-odd-indices number-list 10 ‘even’) The new list: 1 10 8 10 43 10 78 (modify-even-odd-indices number-list 10 ‘odd’) The new list: 10 56 10 1 10 9 10

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  • C# & C++, runtime error when call C++ dll from C#

    - by 5YrsLaterDBA
    I have written a C++ wrapper DLL for C# to call. The DLL was tested and worked fine with my C++ test program. now integrated with C#, I got runtime error and crashed. Cannot use debugger to see more details. The C++ side has only one method: #ifdef DLLWRAPPERWIN32_EXPORTS #define DLLWRAPPERWIN32_API __declspec(dllexport) #else #define DLLWRAPPERWIN32_API __declspec(dllimport) #endif #include "NB_DPSM.h" extern "C" { DLLWRAPPERWIN32_API int WriteGenbenchDataWrapper(string fileNameToAnalyze, string parameterFileName, string baseNameToSaveData, string logFileName, string& message) ; } in the C# side, there is a definition, [DllImport("..\\..\\thirdParty\\cogs\\DLLWrapperWin32.dll")] public static extern int WriteGenbenchDataWrapper(string fileNameToAnalyze, string parameterFileName, string baseNameToSaveData, string logFileName, ref string message); and a call: string msg = ""; int returnVal = WriteGenbenchDataWrapper(rawDataFileName, parameterFileName, outputBaseName, logFileName, ref msg); I guess there must be something wrong with the last parameter of the function. string& in C++ should be ref string in C#?

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  • [Using $this when not in object context in] php error

    - by JasonS
    I have solved this problem, I just need to know what to do. I get the above error because I just realised that the class is being run as class::function($values) instead of class-function($values). Does anyone know how to convert this function to instantiate the class then run the function with values? private function _load($values=null) { define('LOADED_CONTROLLER', $this->controller); define('LOADED_FUNCTION', $this->function); $function = $this->function; $controller = new $this->controller; ($values == null) ? $controller->$function() : call_user_func_array(array($this->controller, $function), $values); }

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  • C++ SDL State Machine Segfault

    - by user1602079
    The code compiles and builds fine, but it immediately segfaults. I've looked at this for a while and have no idea why. Any help is appreciated. Thank you! Here's the code: main.cpp #include "SDL/SDL.h" #include "Globals.h" #include "Core.h" #include "GameStates.h" #include "Introduction.h" int main(int argc, char** args) { if(core.Initilize() == false) { SDL_Quit(); } while(core.desiredstate != core.Quit) { currentstate->EventHandling(); currentstate->Logic(); core.ChangeState(); currentstate->Render(); currentstate->Update(); } SDL_Quit(); } Core.h #ifndef CORE_H #define CORE_H #include "SDL/SDL.h" #include <string> class Core { public: SDL_Surface* Load(std::string filename); void ApplySurface(int X, int Y, SDL_Surface* source, SDL_Surface* destination); void SetState(int newstate); void ChangeState(); enum state { Intro, STATES_NULL, Quit }; int desiredstate, stateID; bool Initilize(); }; #endif Core.cpp #include "Core.h" #include "SDL/SDL.h" #include "Globals.h" #include "Introduction.h" #include <string> /* Initilizes SDL subsystems */ bool Core::Initilize() { //Inits subsystems, reutrns false upon error if(SDL_Init(SDL_INIT_EVERYTHING) == -1) { return false; } SDL_WM_SetCaption("Game", NULL); return true; } /* Loads surfaces and optimizes them */ SDL_Surface* Core::Load(std::string filename) { //The surface to be optimized SDL_Surface* original = SDL_LoadBMP(filename.c_str()); //The optimized surface SDL_Surface* optimized = NULL; //Optimizes the image if it loaded properly if(original != NULL) { optimized = SDL_DisplayFormat(original); SDL_FreeSurface(original); } else { //returns NULL upon error return NULL; } return optimized; } /* Blits surfaces */ void Core::ApplySurface(int X, int Y, SDL_Surface* source, SDL_Surface* destination) { //Stores the coordinates of the surface SDL_Rect offsets; offsets.x = X; offsets.y = Y; //Bits the surface if both surfaces are present if(source != NULL && destination != NULL) { SDL_BlitSurface(source, NULL, destination, &offsets); } } /* Sets desiredstate to newstate */ void Core::SetState(int newstate) { if(desiredstate != Quit) { desiredstate = newstate; } } /* Changes the game state */ void Core::ChangeState() { if(desiredstate != STATES_NULL && desiredstate != Quit) { delete currentstate; switch(desiredstate) { case Intro: currentstate = new Introduction(); break; } stateID = desiredstate; desiredstate = core.STATES_NULL; } } Globals.h #ifndef GLOBALS_H #define GLOBALS_H #include "SDL/SDL.h" #include "Core.h" #include "GameStates.h" extern SDL_Surface* screen; extern Core core; extern GameStates* currentstate; #endif Globals.cpp #include "Globals.h" #include "SDL/SDL.h" #include "GameStates.h" SDL_Surface* screen = SDL_SetVideoMode(640, 480, 32, SDL_SWSURFACE); Core core; GameStates* currentstate = NULL; GameStates.h #ifndef GAMESTATES_H #define GAMESTATES_H class GameStates { public: virtual void EventHandling() = 0; virtual void Logic() = 0; virtual void Render() = 0; virtual void Update() = 0; }; #endif Introduction.h #ifndef INTRODUCTION_H #define INTRODUCTION_H #include "GameStates.h" #include "Globals.h" class Introduction : public GameStates { public: Introduction(); private: void EventHandling(); void Logic(); void Render(); void Update(); ~Introduction(); SDL_Surface* test; }; #endif Introduction.cpp #include "SDL/SDL.h" #include "Core.h" #include "Globals.h" #include "Introduction.h" /* Loads all the assets */ Introduction::Introduction() { test = core.Load("test.bmp"); } void Introduction::EventHandling() { SDL_Event event; while(SDL_PollEvent(&event)) { switch(event.type) { case SDL_QUIT: core.SetState(core.Quit); break; } } } void Introduction::Logic() { //to be coded } void Introduction::Render() { core.ApplySurface(30, 30, test, screen); } void Introduction::Update() { SDL_Flip(screen); } Introduction::~Introduction() { SDL_FreeSurface(test); } Sorry if the formatting is a bit off... Having to put four spaces for it to be put into a code block offset it a bit. I ran it through gdb and this is what I got: Program received signal SIGSEGV, Segmentation fault. 0x0000000000400e46 in main () Which isn't incredibly useful... Any help is appreciated. Thank you!

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  • C++ static classes & shared_ptr memory leaks

    - by HardCoder1986
    Hello! I can't understand why does the following code produce memory leaks (I am using boost::shared_ptr with static class instance). Could someone help me? #include <crtdbg.h> #include <boost/shared_ptr.hpp> using boost::shared_ptr; #define _CRTDBG_MAP_ALLOC #define NEW new(_NORMAL_BLOCK, __FILE__, __LINE__) static struct myclass { static shared_ptr<int> ptr; myclass() { ptr = shared_ptr<int>(NEW int); } } myclass_instance; shared_ptr<int> myclass::ptr; int main() { _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF | _CRTDBG_CHECK_ALWAYS_DF | _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG)); return 0; }

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  • Why this code is not working on linux server ?

    - by user488001
    Hello Experts, I am new in Zend Framework, and this code is use for downloading contents. This code is working in localhost but when i tried to execute in linux server it shows error file not found. public function downloadAnnouncementsAction() { $file= $this-_getParam('file'); $file = str_replace("%2F","/",$this-_getParam('file')); // Allow direct file download (hotlinking)? // Empty - allow hotlinking // If set to nonempty value (Example: example.com) will only allow downloads when referrer contains this text define('ALLOWED_REFERRER', ''); // Download folder, i.e. folder where you keep all files for download. // MUST end with slash (i.e. "/" ) define('BASE_DIR','file_upload'); // log downloads? true/false define('LOG_DOWNLOADS',true); // log file name define('LOG_FILE','downloads.log'); // Allowed extensions list in format 'extension' => 'mime type' // If myme type is set to empty string then script will try to detect mime type // itself, which would only work if you have Mimetype or Fileinfo extensions // installed on server. $allowed_ext = array ( // audio 'mp3' => 'audio/mpeg', 'wav' => 'audio/x-wav', // video 'mpeg' => 'video/mpeg', 'mpg' => 'video/mpeg', 'mpe' => 'video/mpeg', 'mov' => 'video/quicktime', 'avi' => 'video/x-msvideo' ); // If hotlinking not allowed then make hackers think there are some server problems if (ALLOWED_REFERRER !== '' && (!isset($_SERVER['HTTP_REFERER']) || strpos(strtoupper($_SERVER['HTTP_REFERER']),strtoupper(ALLOWED_REFERRER)) === false) ) { die("Internal server error. Please contact system administrator."); } // Make sure program execution doesn't time out // Set maximum script execution time in seconds (0 means no limit) set_time_limit(0); if (!isset($file) || empty($file)) { die("Please specify file name for download."); } // Nullbyte hack fix if (strpos($file, "\0") !== FALSE) die(''); // Get real file name. // Remove any path info to avoid hacking by adding relative path, etc. $fname = basename($file); // Check if the file exists // Check in subfolders too function find_file ($dirname, $fname, &$file_path) { $dir = opendir($dirname); while ($file = readdir($dir)) { if (empty($file_path) && $file != '.' && $file != '..') { if (is_dir($dirname.'/'.$file)) { find_file($dirname.'/'.$file, $fname, $file_path); } else { if (file_exists($dirname.'/'.$fname)) { $file_path = $dirname.'/'.$fname; return; } } } } } // find_file // get full file path (including subfolders) $file_path = ''; find_file(BASE_DIR, $fname, $file_path); if (!is_file($file_path)) { die("File does not exist. Make sure you specified correct file name."); } // file size in bytes $fsize = filesize($file_path); // file extension $fext = strtolower(substr(strrchr($fname,"."),1)); // check if allowed extension if (!array_key_exists($fext, $allowed_ext)) { die("Not allowed file type."); } // get mime type if ($allowed_ext[$fext] == '') { $mtype = ''; // mime type is not set, get from server settings if (function_exists('mime_content_type')) { $mtype = mime_content_type($file_path); } else if (function_exists('finfo_file')) { $finfo = finfo_open(FILEINFO_MIME); // return mime type $mtype = finfo_file($finfo, $file_path); finfo_close($finfo); } if ($mtype == '') { $mtype = "application/force-download"; } } else { // get mime type defined by admin $mtype = $allowed_ext[$fext]; } // Browser will try to save file with this filename, regardless original filename. // You can override it if needed. if (!isset($_GET['fc']) || empty($_GET['fc'])) { $asfname = $fname; } else { // remove some bad chars $asfname = str_replace(array('"',"'",'\\','/'), '', $_GET['fc']); if ($asfname === '') $asfname = 'NoName'; } // set headers header("Pragma: public"); header("Expires: 0"); header("Cache-Control: must-revalidate, post-check=0, pre-check=0"); header("Cache-Control: public"); header("Content-Description: File Transfer"); header("Content-Type: $mtype"); header("Content-Disposition: attachment; filename=\"$asfname\""); header("Content-Transfer-Encoding: binary"); header("Content-Length: " . $fsize); // download // @readfile($file_path); $file = @fopen($file_path,"rb"); if ($file) { while(!feof($file)) { print(fread($file, 1024*8)); flush(); if (connection_status()!=0) { @fclose($file); die(); } } @fclose($file); } // log downloads if (!LOG_DOWNLOADS) die(); $f = @fopen(LOG_FILE, 'a+'); if ($f) { @fputs($f, date("m.d.Y g:ia")." ".$_SERVER['REMOTE_ADDR']." ".$fname."\n"); @fclose($f); } } please Help...

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  • Declare Locally or Globally in Delphi?

    - by lkessler
    I have a procedure my program calls tens of thousands of times that uses a generic structure like this: procedure PrintIndiEntry(JumpID: string); type TPeopleIncluded = record IndiPtr: pointer; Relationship: string; end; var PeopleIncluded: TList<TPeopleIncluded>; PI: TPeopleIncluded; begin { PrintIndiEntry } PeopleIncluded := TList<TPeopleIncluded>.Create; { A loop here that determines a small number (up to 100) people to process } while ... do begin PI.IndiPtr := ...; PI.Relationship := ...; PeopleIncluded.Add(PI); end; DoSomeProcess(PeopleIncluded); PeopleIncluded.Clear; PeopleIncluded.Free; end { PrintIndiEntry } Alternatively, I can declare PeopleIncluded globally rather than locally as follows: unit process; interface type TPeopleIncluded = record IndiPtr: pointer; Relationship: string; end; var PeopleIncluded: TList<TPeopleIncluded>; PI: TPeopleIncluded; procedure PrintIndiEntry(JumpID: string); begin { PrintIndiEntry } { A loop here that determines a small number (up to 100) people to process } while ... do begin PI.IndiPtr := ...; PI.Relationship := ...; PeopleIncluded.Add(PI); end; DoSomeProcess(PeopleIncluded); PeopleIncluded.Clear; end { PrintIndiEntry } procedure InitializeProcessing; begin PeopleIncluded := TList<TPeopleIncluded>.Create; end; procedure FinalizeProcessing; begin PeopleIncluded.Free; end; My question is whether in this situation it is better to declare PeopleIncluded globally rather than locally. I know the theory is to define locally whenever possible, but I would like to know if there are any issues to worry about with regards to doing tens of thousands of of "create"s and "free"s? Making them global will do only one create and one free. What is the recommended method to use in this case? If the recommended method is to still define it locally, then I'm wondering if there are any situations where it is better to define globally when defining locally is still an option.

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  • Preprocessor directive #ifndef for C/C++ code

    - by Leif Andersen
    In eclipse, whenever I create a new C++ class, or C header file, I get the following type of structure. Say I create header file example.h, I get this: /*Comments*/ #ifndef EXAMPLE_H_ #define EXAMPLE_H_ /* Place to put all of my definitions etc. */ #endif I think ifndef is saying that if EXAMPLE_H_ isn't defined, define it, which may be useful depending on what tool you are using to compile and link your project. However, I have two questions: Is this fairly common? I don't see it too often. And is it a good idea to use that rubric, or should you just jump right into defining your code. What is EXAMPLE_H_ exactly? Why not example.h, or just example? Is there anything special about that, or could is just be an artifact of how eclipse prefers to autobuild projects? Thank you for your help.

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  • How to use #ifdef entities as part of functions in header files

    - by Crazyjavahacking
    I would like to ask if it is possible to use the entities defined in #ifdef block in header files. To be clear, I have following code: #ifdef #include <winsock2.h> #define SOCKET_HANDLE SOCKET #define CONNECTION_HANDLE SOCKET #endif SOCKET_HANDLE createServerSocket(const char* hostAddress, short port); I am Java developer and this seems completely fine for me. However compiler has a problem with this. Can you explain why is that code a problem? Also how can I force to compile it. (The idea is to have generic interface and conditional compilation to determine real types according to running platform at compile time.) Thanks

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  • How can I make Church numerals more human readable in lisp?

    - by Jason Baker
    I can define church numerals fairly easy using scheme: > (define f (lambda (x) x)) > (f f) ;0 #<procedure:f> > (f (f f)) ;1 #<procedure:f> However, this doesn't make it very easy to recognize that (f f) is 0 and (f (f f)) is 1. Is there a way that I can make these numerals more readable? What would be ideal is this: > (f f) 0 > (f (f f)) 1 The example is in scheme, but I'll take an answer in any lisp.

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  • Understanding linear linked list

    - by ArtWorkAD
    Hi, I have some problems understanding the linear linked list data structure. This is how I define a list element: class Node{ Object data; Node link; public Node(Object pData, Node pLink){ this.data = pData; this.link = pLink; } } To keep it simple we say that a list are linked nodes so we do not need to define a class list (recursion principle). My problem is that I am really confused in understanding how nodes are connected, more precisely the sequence of the nodes when we connect them. Node n1 = new Node(new Integer(2), null); Node n2 = new Node(new Integer(1), n1); What is link? Is it the previous or the next element? Any other suggestions to help me understanding this data structure?

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  • WiX, Conditionally installing a file based on OS

    - by Sam Saffron
    In my WiX project I need to install different content for the same file name, based on the OS. If the OS is Windows 7 then the file needs to have content X. If the OS is Windows Vista the file needs to have content Y. I have thought through a few approaches: Define two components, one with the content for windows 7 and another with the contents for Vista. Run a custom action based on the OS that overwrites the content for Vista if the OS is Windows 7. Define two additional features (window7 config and win vista config) have the components target the same file and install the feature conditionally based on OS. Which is the best approach to take. Any tips, tricks and sample wix to get this going?

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  • Template class + virtual function = must implement?

    - by sold
    This code: template <typename T> struct A { T t; void DoSomething() { t.SomeFunction(); } }; struct B { }; A<B> a; is easily compiled without any complaints, as long as I never call a.DoSomething(). However, if I define DoSomething as a virtual function, I will get a compile error saying that B doesn't declare SomeFunction. I can somewhat see why it happens (DoSomething should now have an entry in the vtable), but I can't help feeling that it's not really obligated. Plus it sucks. Is there any way to overcome this? EDIT 2: Okay. I hope this time it makes sence: Let's say I am doing intrusive ref count, so all entities must inherit from base class Object. How can I suuport primitive types too? I can define: template <typename T> class Primitive : public Object { T value; public: Primitive(const T &value=T()); operator T() const; Primitive<T> &operator =(const T &value); Primitive<T> &operator +=(const T &value); Primitive<T> &operator %=(const T &value); // And so on... }; so I can use Primitive<int>, Primitive<char>... But how about Primitive<float>? It seems like a problem, because floats don't have a %= operator. But actually, it isn't, since I'll never call operator %= on Primitive<float>. That's one of the deliberate features of templates. If, for some reason, I would define operator %= as virtual. Or, if i'll pre-export Primitive<float> from a dll to avoid link errors, the compiler will complain even if I never call operator %= on a Primitive<float>. If it would just have fill in a dummy value for operator %= in Primitive<float>'s vtable (that raises an exception?), everything would have been fine.

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  • Should the include guards be unique even between namespaces?

    - by Arun
    I am using same class name in two namespaces, say A and B. Should the include guards be unique while declaring the classes with different namespaces too? I mean can't there be two files names AFile.h (in different directories) with same include guards and declaring different namespaces? File 1: #ifndef AFILE_H #define AFILE_H namespace A { class CAFile {... }; }; #endif File 2: #ifndef AFILE_H #define AFILE_H namespace B { class CAFile {... }; }; #endif

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  • Pointer to another classs as a property

    - by arjacsoh
    Why I receive an error when I try to create a property to another class through a pointer like that: #ifndef SQUARE_H #define SQUARE_H #include <string> //using namespace std; #include "Player.h" class Square { public: Square(int); void process(); protected: int ID; Player* PlayerOn; <--- }; #endif and the Player class is : #ifndef PLAYER_H #define PLAYER_H #include <string> //using namespace std; #include "Square.h" class Player { public: Player(int,int); // ~Player(void); int playDice(); private: int ID; int money; }; #endif I receive: syntax error missing ; before * (on the declaration of Player* PlayerOn;) and missing type specifier (on the same line...)

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  • How to increment a value using a C-Preprocessor?

    - by mystify
    Example: I try to do this: static NSInteger stepNum = 1; #define METHODNAME(i) -(void)step##i #define STEP METHODNAME(stepNum++) @implementation Test STEP { // do stuff... [self nextFrame:@selector(step2) afterDelay:1]; } STEP { // do stuff... [self nextFrame:@selector(step3) afterDelay:1]; } STEP { // do stuff... [self nextFrame:@selector(step4) afterDelay:1]; } // ... When building, Xcode complains that it can't increment stepNum. This seems logical to me, because at this time the code is not "alive" and this pre-processing substitution stuff happens before actually compiling the source code. Is there another way I could have an variable be incremented on every usage of STEP macro, the easy way?

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  • crc24 from c to python

    - by biiiiiaw
    can someone please translate this code to python? i have tried and tried again, but have not managed it: #define CRC24_INIT 0xB704CEL #define CRC24_POLY 0x1864CFBL typedef long crc24; crc24 crc_octets(unsigned char *octets, size_t len) { crc24 crc = CRC24_INIT; int i; while (len--) { crc ^= (*octets++) << 16; for (i = 0; i < 8; i++) { crc <<= 1; if (crc & 0x1000000) crc ^= CRC24_POLY; } } return crc & 0xFFFFFFL; } i have the rotate left function (ROL24(value,bits_to_rotate_by)), which i know works since i got it from a source code of a reputable programmer, but i dont get the * and ++ on octet. i only sort of understand how ++ works in c++, and i dont know what * is at all

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  • Is the "==" operator required to be defined to use std::find

    - by user144182
    Let's say I have: class myClass std::list<myClass> myList where myClass does not define the == operator and only consists of public fields. In both VS2010 and VS2005 the following does not compile: myClass myClassVal = myList.front(); std::find( myList.begin(), myList.end(), myClassVal ) complaining about lack of == operator. I naively assumed it would do a value comparison of the myClass object's public members, but I am almost positive this is not correct. I assume if I define a == operator or perhaps use a functor instead, it will solve the problem. Alternatively, if my list was holding pointers instead of values, the comparison would work. Is this right or should I be doing something else?

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  • In PLT scheme, can I export functions after another function has been called?

    - by Jason Baker
    I'm trying to create a binding to libpython using scheme's FFI. To do this, I have to get the location of python, create the ffi-lib, and then create functions from it. So for instance I could do this: (module pyscheme scheme (require foreign) (unsafe!) (define (link-python [lib "/usr/lib/libpython2.6.so"]) (ffi-lib lib)) This is all well and good, but I can't think of a way to export functions. For instance, I could do something like this: (define Py_Initialize (get-ffi-obj "Py_Initialize" libpython (_fun -> _void))) ...but then I'd have to store a reference to libpython (created by link-python) globally somehow. Is there any way to export these functions once link-python is called? In other words, I'd like someone using the module to be able to do this: (require pyscheme) (link-python) (Py_Initialize) ...or this: (require pyscheme) (link-python "/weird/location/for/libpython.so") (Py_Initialize) ...but have this give an error: (require pyscheme) (Py_Initialize) How can I do this?

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