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  • Callback function and function pointer trouble in C++ for a BST

    - by Brendon C.
    I have to create a binary search tree which is templated and can deal with any data types, including abstract data types like objects. Since it is unknown what types of data an object might have and which data is going to be compared, the client side must create a comparison function and also a print function (because also not sure which data has to be printed). I have edited some C code which I was directed to and tried to template, but I cannot figure out how to configure the client display function. I suspect variable 'tree_node' of class BinarySearchTree has to be passed in, but I am not sure how to do this. For this program I'm creating an integer binary search tree and reading data from a file. Any help on the code or the problem would be greatly appreciated :) Main.cpp #include "BinarySearchTreeTemplated.h" #include <iostream> #include <fstream> #include <string> using namespace std; /*Comparison function*/ int cmp_fn(void *data1, void *data2) { if (*((int*)data1) > *((int*)data2)) return 1; else if (*((int*)data1) < *((int*)data2)) return -1; else return 0; } static void displayNode() //<--------NEED HELP HERE { if (node) cout << " " << *((int)node->data) } int main() { ifstream infile("rinput.txt"); BinarySearchTree<int> tree; while (true) { int tmp1; infile >> tmp1; if (infile.eof()) break; tree.insertRoot(tmp1); } return 0; } BinarySearchTree.h (a bit too big to format here) http://pastebin.com/4kSVrPhm

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  • Does it ever make sense to make a fundamental (non-pointer) parameter const?

    - by Scott Smith
    I recently had an exchange with another C++ developer about the following use of const: void Foo(const int bar); He felt that using const in this way was good practice. I argued that it does nothing for the caller of the function (since a copy of the argument was going to be passed, there is no additional guarantee of safety with regard to overwrite). In addition, doing this prevents the implementer of Foo from modifying their private copy of the argument. So, it both mandates and advertises an implementation detail. Not the end of the world, but certainly not something to be recommended as good practice. I'm curious as to what others think on this issue. Edit: OK, I didn't realize that const-ness of the arguments didn't factor into the signature of the function. So, it is possible to mark the arguments as const in the implementation (.cpp), and not in the header (.h) - and the compiler is fine with that. That being the case, I guess the policy should be the same for making local variables const. One could make the argument that having different looking signatures in the header and source file would confuse others (as it would have confused me). While I try to follow the Principle of Least Astonishment with whatever I write, I guess it's reasonable to expect developers to recognize this as legal and useful.

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  • Modify existing struct alignment in Visual C++

    - by Crend King
    Is there a way to modify the member alignment of an existing struct in Visual C++? Here is the background: I use an 3rd-party library, which uses several structs. To fill up the structs, I pass the address of the struct instance to some functions. Unfortunately, the functions only returns unaligned buffer, so that data of some members are always wrong. /Zp is out of choice, since it breaks the other parts of the program. I know #pragma pack modifies the alignment of the following struct, but I do not want to copy the structs into my code, for the definitions in the library might change in the future. Sample code: test.h: struct am_aligned { BYTE data1[10]; ULONG data2; }; test.cpp: include "test.h" // typedef alignment(1) struct am_aligned am_unaligned int APIENTRY wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPTSTR lpCmdLine, int nCmdShow) { char buffer[20] = {}; for (int i = 0; i < sizeof(unaligned_struct); i++) { buffer[i] = i; } am_aligned instance = *(am_aligned*) buffer; return 0; } instance.data2 is 0x0f0e0d0c, while 0x0d0c0b0a is desired. The commented line does not work of course. Thanks for help!

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  • Putting all methods in class definition

    - by Amnon
    When I use the pimpl idiom, is it a good idea to put all the methods definitions inside the class definition? For example: // in A.h class A { class impl; boost::scoped_ptr<impl> pimpl; public: A(); int foo(); } // in A.cpp class A::impl { // method defined in class int foo() { return 42; } // as opposed to only declaring the method, and defining elsewhere: float bar(); }; A::A() : pimpl(new impl) { } int A::foo() { return pimpl->foo(); } As far as I know, the only problems with putting a method definition inside a class definition is that (1) the implementation is visible in files that include the class definition, and (2) the compiler may make the method inline. These are not problems in this case since the class is defined in a private file, and inlining has no effect since the methods are called in only one place. The advantage of putting the definition inside the class is that you don't have to repeat the method signature. So, is this OK? Are there any other issues to be aware of?

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  • GNU/Linux developement n00b needs help porting C++ application from windows to GNU/Linux.

    - by AndrejaKo
    Hi! These questions may not be perfectly suited for this site, so I apologize in advance for asking them here. I'm trying to port a computer game from windows to GNU/Linux. It uses Ogre3D,CEGUI, ogreogg and ogrenewt. As far as I know all dependencies work on GNU/Linux and in the game itself there is no ooze-specific code. Here's the questions part: Is there any easy way to port visual studio 2008 project to GNU/Linux tool-chain? How do I manage dependencies? In Visual Studio, I'd just add them in property sheets or default directories. I assume on GNU/Linux autoconf and make take care of that, but in which way? Do I have to add each .cpp and .hpp manually or is there some way to automate things? How do I solve the problem of dependencies on different locations on different systems? I'd like to use Eclipse as IDE under GNU/Linux. I know that the best answer to most of my questions is RTFM, but I'm not sure what I exactly need and where to start looking.

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  • Howcome some C++ functions with unspecified linkage build with C linkage?

    - by christoffer
    This is something that makes me fairly perplexed. I have a C++ file that implements a set of functions, and a header file that defines prototypes for them. When building with Visual Studio or MingW-gcc, I get linking errors on two of the functions, and adding an 'extern "C"' qualifier resolved the error. How is this possible? Header file, "some_header.h": // Definition of struct DEMO_GLOBAL_DATA omitted DWORD WINAPI ThreadFunction(LPVOID lpData); void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen); void CheckValid(DEMO_GLOBAL_DATA *pData); int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName); void HandleEnd(DEMO_GLOBAL_DATA *pData); C++ file, "some_implementation.cpp" #include "some_header.h" DWORD WINAPI ThreadFunction(LPVOID lpData) { /* omitted */ } void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen) { /* omitted */ } void CheckValid(DEMO_GLOBAL_DATA *pData) { /* omitted */ } int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName) { /* omitted */ } void HandleEnd(DEMO_GLOBAL_DATA *pData) { /* omitted */ } The implementations compile without warnings, but when linking with the UI code that calls these, I get a normal error LNK2001: unresolved external symbol "int __cdecl HandleStart(struct _DEMO_GLOBAL_DATA *, wchar_t *) error LNK2001: unresolved external symbol "void __cdecl CheckValid(struct _DEMO_MAIN_GLOBAL_DATA * What really confuses me, now, is that only these two functions (HandleStart and CheckValid) seems to be built with C linkage. Explicitly adding "extern 'C'" declarations for only these two resolved the linking error, and the application builds and runs. Adding "extern 'C'" on some other function, such as HandleEnd, introduces a new linking error, so that one is obviously compiled correctly. The implementation file is never modified in any of this, only the prototypes.

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  • Creating a new object destroys an older object with different name in C++

    - by Mikael
    First question here! So, I am having some problems with pointers in Visual C++ 2008. I'm writing a program which will control six cameras and do some processing on them so to clean things up I have created a Camera Manager class. This class handles all operations which will be carried out on all the cameras. Below this is a Camera class which interacts with each individual camera driver and does some basic image processing. Now, the idea is that when the manager is initialised it creates two cameras and adds them to a vector so that I can access them later. The catch here is that when I create the second camera (camera2) the first camera's destructor is called for some reason, which then disconnects the camera. Normally I'd assume that the problem is somewhere in the Camera class, but in this case everything works perfectly as long as I don't create the camera2 object. What's gone wrong? CameraManager.h: #include "stdafx.h" #include <vector> #include "Camera.h" class CameraManager{ std::vector<Camera> cameras; public: CameraManager(); ~CameraManager(); void CaptureAll(); void ShowAll(); }; CameraManager.cpp: #include "stdafx.h" #include "CameraManager.h" CameraManager::CameraManager() { printf("Camera Manager: Initializing\n"); [...] Camera *camera1 = new Camera(NodeInfo,1, -44,0,0); cameras.push_back(*camera1); // Adding the following two lines causes camera1's destructor to be called. Why? Camera *camera2 = new Camera(NodeInfo,0, 44,0,0); cameras.push_back(*camera2); printf("Camera Manager: Ready\n"); }

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  • Enumeration trouble: redeclared as different kind of symbol

    - by Matt
    Hello all. I am writing a program that is supposed to help me learn about enumeration data types in C++. The current trouble is that the compiler doesn't like my enum usage when trying to use the new data type as I would other data types. I am getting the error "redeclared as different kind of symbol" when compiling my trangleShape function. Take a look at the relevant code. Any insight is appreciated! Thanks! (All functions are their own .cpp files.) header file #ifndef HEADER_H_INCLUDED #define HEADER_H_INCLUDED #include <iostream> #include <iomanip> using namespace std; enum triangleType {noTriangle, scalene, isoceles, equilateral}; //prototypes void extern input(float&, float&, float&); triangleType extern triangleShape(float, float, float); /*void extern output (float, float, float);*/ void extern myLabel(const char *, const char *); #endif // HEADER_H_INCLUDED main function //8.1 main // this progam... #include "header.h" int main() { float sideLength1, sideLength2, sideLength3; char response; do //main loop { input (sideLength1, sideLength2, sideLength3); triangleShape (sideLength1, sideLength2, sideLength3); //output (sideLength1, sideLength2, sideLength3); cout << "\nAny more triangles to analyze? (y,n) "; cin >> response; } while (response == 'Y' || response == 'y'); myLabel ("8.1", "2/11/2011"); return 0; } triangleShape shape # include "header.h" triangleType triangleShape(sideLenght1, sideLength2, sideLength3) { triangleType triangle; return triangle; }

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  • #include - brackets vs quotes in XCode?

    - by Chris Becke
    In MSVC++ #include files are searched for differently depending on whether the file is enclosed in "" or <. The quoted form searches first in the local folder, then in /I specified locations, The angle bracket form avoids the local folder. This means, in MSVC++, its possible to have header files with the same name as runtime and SDK headers. So, for example, I need to wrap up the windows sdk windows.h file to undefine some macro's that cause trouble. With MSVS I can just add a (optional) windows.h file to my project as long as I include it using the quoted form :- // some .cpp file #include "windows.h" // will include my local windows.h file And in my windows.h, I can pull in the real one using the angle bracket form: // my windows.h #include <windows.h> // will load the real one #undef ConflictingSymbol Trying this trick with GCC in XCode didn't work. angle bracket #includes in system header files in fact are finding my header files with similar names in my local folder structure. The MSVC system means its quite safe to have a "String.h" header file in my own folder structre. On XCode this seems to be a major no no. Is there some way to control this search path behaviour in XCode to be more like MSVC's? Or do I just have to avoid naming any of my headers anything that might possibly conflict with a system header. Writing cross platform code and using lots of frameworks means the possibility of incidental conflicts seems large.

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  • CURL C API: callback was not called

    - by Pierre
    Hi all, The code below is a test for the CURL C API . The problem is that the callback function write_callback is never called. Why ? /** compilation: g++ source.cpp -lcurl */ #include <assert.h> #include <iostream> #include <cstdlib> #include <cstring> #include <cassert> #include <curl/curl.h> using namespace std; static size_t write_callback(void *ptr, size_t size, size_t nmemb, void *userp) { std::cerr << "CALLBACK WAS CALLED" << endl; exit(-1); return size*nmemb; } static void test_curl() { int any_data=1; CURLM* multi_handle=NULL; CURL* handle_curl = ::curl_easy_init(); assert(handle_curl!=NULL); ::curl_easy_setopt(handle_curl, CURLOPT_URL, "http://en.wikipedia.org/wiki/Main_Page"); ::curl_easy_setopt(handle_curl, CURLOPT_WRITEDATA, &any_data); ::curl_easy_setopt(handle_curl, CURLOPT_VERBOSE, 1); ::curl_easy_setopt(handle_curl, CURLOPT_WRITEFUNCTION, write_callback); ::curl_easy_setopt(handle_curl, CURLOPT_USERAGENT, "libcurl-agent/1.0"); multi_handle = ::curl_multi_init(); assert(multi_handle!=NULL); ::curl_multi_add_handle(multi_handle, handle_curl); int still_running=0; /* lets start the fetch */ while(::curl_multi_perform(multi_handle, &still_running) == CURLM_CALL_MULTI_PERFORM ); std::cerr << "End of curl_multi_perform."<< endl; //cleanup should go here ::exit(EXIT_SUCCESS); } int main(int argc,char** argv) { test_curl(); return 0; } Many thanks Pierre

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  • Getting functions of inherited functions to be called

    - by wrongusername
    Let's say I have a base class Animal from which a class Cow inherits, and a Barn class containing an Animal vector, and let's say the Animal class has a virtual function scream(), which Cow overrides. With the following code: Animal.h #ifndef _ANIMAL_H #define _ANIMAL_H #include <iostream> using namespace std; class Animal { public: Animal() {}; virtual void scream() {cout << "aaaAAAAAAAAAAGHHHHHHHHHH!!! ahhh..." << endl;} }; #endif /* _ANIMAL_H */ Cow.h #ifndef _COW_H #define _COW_H #include "Animal.h" class Cow: public Animal { public: Cow() {} void scream() {cout << "MOOooooOOOOOOOO!!!" << endl;} }; #endif /* _COW_H */ Barn.h #ifndef _BARN_H #define _BARN_H #include "Animal.h" #include <vector> class Barn { std::vector<Animal> animals; public: Barn() {} void insertAnimal(Animal animal) {animals.push_back(animal);} void tortureAnimals() { for(int a = 0; a < animals.size(); a++) animals[a].scream(); } }; #endif /* _BARN_H */ and finally main.cpp #include <stdlib.h> #include "Barn.h" #include "Cow.h" #include "Chicken.h" /* * */ int main(int argc, char** argv) { Barn barn; barn.insertAnimal(Cow()); barn.tortureAnimals(); return (EXIT_SUCCESS); } I get this output: aaaAAAAAAAAAAGHHHHHHHHHH!!! ahhh... How should I code this to get MOOooooOOOOOOOO!!! (and whatever other classes inheriting Animal wants scream() to be) instead?

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  • Can a custom MFC window/dialog be a class template instantiation?

    - by John
    There's a bunch of special macros that MFC uses when creating dialogs, and in my quick tests I'm getting weird errors trying to compile a template dialog class. Is this likely to be a big pain to achieve? Here's what I tried: MyDlg.h template <class W> class CMyDlg : public CDialog { typedef CDialog super; DECLARE_DYNAMIC(CMyDlg <W>) public: CMyDlg (CWnd* pParent); // standard constructor virtual ~CMyDlg (); // Dialog Data enum { IDD = IDD_MYDLG }; protected: virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support DECLARE_MESSAGE_MAP() private: W *m_pWidget; //W will always be a CDialog }; IMPLEMENT_DYNAMIC(CMyDlg<W>, super) <------------------- template <class W> CMyDlg<W>::CMyDlg(CWnd* pParent) : super(CMyDlg::IDD, pParent) { m_pWidget = new W(this); } I get a whole bunch of errors but main one appears to be: error C2955: 'CMyDlg' : use of class template requires template argument list I tried using some specialised template versions of macros but it doesn't help much, other errors change but this one remains. Note my code is all in one file, since C++ templates don't like .h/.cpp like normal. I'm assuming someone must have done this in the past, possibly creating custom versions of macros, but I can't find it by searching, since 'template' has other meanings.

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  • no instance of overloaded function getline c++

    - by Dave
    I'm a bit confused as to what i have incorrect with my script that is causing this error. I have a function which calls a fill for game settings but it doesn't like my getline. Also i should mention these are the files i have included for it: #include <fstream> #include <cctype> #include <map> #include <iostream> #include <string> #include <algorithm> #include <vector> using namespace std;' This is what i have: std::map<string, string> loadSettings(std::string file){ ifstream file(file); string line; std::map<string, string> config; while(std::getline(file, line)) { int pos = line.find('='); if(pos != string::npos) { string key = line.substr(0, pos); string value = line.substr(pos + 1); config[trim(key)] = trim(value); } } return (config); } The function is called like this from my main.cpp //load settings for game std::map<string, string> config = loadSettings("settings.txt"); //load theme for game std::map<string, string> theme = loadSettings("theme.txt"); Where did i go wrong ? Please help! The error: settings.h(61): error C2784: 'std::basic_istream<_Elem,_Traits> &std::getline(std::basic_istream<_Elem,_Traits> &&,std::basic_string<_Elem,_Traits,_Alloc> &)' : could not deduce template argument for 'std::basic_istream<_Elem,_Traits> &&' from 'std::string'

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  • Best way to organize a Go interface

    - by Metropolis
    Hey Everyone, Its been a long time since I have programmed in C++, and if I remember correctly the best way to organize classes was to create your class in the .h file, and then your implementation in your .cpp file. Well I am trying to learn Go now and I was reading over the Go for C++ Programmers article when I came upon interfaces. The article explains that interfaces in Go essentially take the place of classes, and shows how to set them up pretty well. What I am trying to figure out though is how should I organize an interface into files? For instance, should the interface be in one file while the implementation is in another? myInterface.go type myInterface interface { get() int set(i int) } myImplementation.go type myType struct { i int } func (p *myType) set(i int) { p.i = i } func (p *myType) get() int { return p.i } My code here may be wrong since I do not completely know what I am doing yet (and if I am wrong please correct me), but would this be the best way to set this up? Im having a very hard time trying to wrap my head around how to organize code in Go so any help is appreciated! Metropolis

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  • Programmatically parse and edit C++ Source Files

    - by Kryten
    Hi, I want to able programmatically parse and edit C++ source files. I need to be able to change/add code in certain sections of code (i.e. in functions, class blocks, etc). I would also (preferably) be able to get comments as well. Part of what I want to do can be explained by the following piece of code: CPlusPlusSourceParser cp = new CPlusPlusSourceParser(“x.cpp”); // Create C++ Source Parser Object CPlusPlusSourceFunction[] funcs = cp.getFunctions(); // Get all the functions for (int i = 0; i &lt funcs.length; i++) { // Loop through all functions funcs[i].append(/* … code I want to append …*/); // Append some code to function } cp.save(); // Save new source cp.close(); // Close file How can I do that? I’d like to be able to do this preferably in Java, C++, Perl, Python or C#. However, I am open to other language API’s.

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  • C header file won't compile with C, but will with C++.

    - by Leif Andersen
    I have the following chunk of a header file BKE_mesh.h: /* Connectivity data */ typedef struct IndexNode { struct IndexNode *next, *prev; int index; } IndexNode; void create_vert_face_map(ListBase **map, IndexNode **mem, const struct MFace *mface, const int totvert, const int totface); void create_vert_edge_map(ListBase **map, IndexNode **mem, const struct MEdge *medge, const int totvert, const int totedge); Note that the header file was prepared for the possibility of being used in a C++ file, as it had: #ifdef __cplusplus extern "C" { #endif at the top of the file, and the needed finish at the bottom. But the class implementing it was written in C. Next, whenever I try to #include the header file, I get an odd error. If the file has a .cpp extension, it compiles just fine, no complaints whatsoever. However, if I do: #include "BKE_mesh.h" inside of a file with a .c extension, I get the following errors: expected ')' before '*' token for the two last functions, in specific, the variable: ListBase **map in both classes. (Note that earlier in the header file, it declared, but not defined ListBase). So, my question is: why is this valid C++ code, but not C code? Thank you.

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  • A public struct inside a class

    - by Koning Baard
    I am new to C++, and let's say I have two classes: Creature and Human: /* creature.h */ class Creature { private: public: struct emotion { /* All emotions are percentages */ char joy; char trust; char fear; char surprise; char sadness; char disgust; char anger; char anticipation; char love; }; }; /* human.h */ class Human : Creature { }; And I have this in my main function in main.cpp: Human foo; My question is: how can I set foo's emotions? I tried this: foo->emotion.fear = 5; But GCC gives me this compile error: error: base operand of '-' has non-pointer type 'Human' This: foo.emotion.fear = 5; Gives: error: 'struct Creature::emotion' is inaccessible error: within this context error: invalid use of 'struct Creature::emotion' Can anyone help me? Thanks P.S. No I did not forget the #includes

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  • GetIpAddrTable() leaks memory. How to resolve that?

    - by Stabledog
    On my Windows 7 box, this simple program causes the memory use of the application to creep up continuously, with no upper bound. I've stripped out everything non-essential, and it seems clear that the culprit is the Microsoft Iphlpapi function "GetIpAddrTable()". On each call, it leaks some memory. In a loop (e.g. checking for changes to the network interface list), it is unsustainable. There seems to be no async notification API which could do this job, so now I'm faced with possibly having to isolate this logic into a separate process and recycle the process periodically -- an ugly solution. Any ideas? // IphlpLeak.cpp - demonstrates that GetIpAddrTable leaks memory internally: run this and watch // the memory use of the app climb up continuously with no upper bound. #include <stdio.h> #include <windows.h> #include <assert.h> #include <Iphlpapi.h> #pragma comment(lib,"Iphlpapi.lib") void testLeak() { static unsigned char buf[16384]; DWORD dwSize(sizeof(buf)); if (GetIpAddrTable((PMIB_IPADDRTABLE)buf, &dwSize, false) == ERROR_INSUFFICIENT_BUFFER) { assert(0); // we never hit this branch. return; } } int main(int argc, char* argv[]) { for ( int i = 0; true; i++ ) { testLeak(); printf("i=%d\n",i); Sleep(1000); } return 0; }

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  • In C/C++ mode in Emacs, change face of code in #if 0...#endif block to comment face

    - by pogopop77
    I'm trying to add functionality found in some other code editors to my Emacs configuration, whereby C/C++ code within #if 0...#endif blocks is automatically set to the comment face/font. Based on my testing, cpp-highlight-mode does something like what I want, but requires user action. It seems like tying into the font-lock functionality is the correct option to make the behavior automatic. I have successfully followed examples in the GNU documentation to change the face of single-line regular expressions. For example: (add-hook 'c-mode-common-hook (lambda () (font-lock-add-keywords nil '(("\\<\\(FIXME\\|TODO\\|HACK\\|fixme\\|todo\\|hack\\)" 1 font-lock-warning-face t))))) works fine to highlight debug related keywords anywhere in a file. However, I am having problems matching #if 0...#endif as a multiline regular expression. I found some useful information in this post (How to compose region like ""), that suggested that Emacs must be told specifically to allow for multiline matches. But this code: (add-hook 'c-mode-common-hook (lambda () '(progn (setq font-lock-multiline t) (font-lock-add-keywords nil '(("#if 0\\(.\\|\n\\)*?#endif" 1 font-lock-comment-face t)))))) still does not work for me. Perhaps my regular expression is wrong (though it appears to work using M-x re-builder), I've messed up my syntax, or I'm following the wrong approach entirely. I'm using Aquamacs 2.1 (which is based on GNU Emacs 23.2.50.1) on OS X 10.6.5, if that makes a difference. Any assistance would be appreciated!

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  • [c++] - Help about class and error: C3861

    - by Chelsea_cole
    Can someone help me in this error? in "cDef.h" : #pragma once class cDef { public: static int STATE_LOGO; static int STATE_MENU; static int MESSAGE_ENTER; static int MESSAGE_UPDATE; static int MESSAGE_PAINT; static int MESSAGE_EXIT; }; in "GameState.h": #pragma once #ifndef _GameState_ #define _GameState_ #include "cDef.h" class MainGame; class GameState; class GameState { public: MainGame *mg; int GAME_STATE_DEF; virtual void MessengeEnter(int message) = 0; virtual void MessengeUpdate(int message,int keys) = 0; virtual void MessengePaint(int message,CDC *pDc) = 0; void StateHandler(int message,CDC *pDc,int keys); public: GameState(void); public: ~GameState(void); }; #endif in "GameState.cpp": #include "StdAfx.h" #include "GameState.h" GameState::GameState(void) { GAME_STATE_DEF = -1; } GameState::~GameState(void) { } void GameState::StateHandler(int message,CDC *pDc,int keys) { if(message == cDef.MESSAGE_ENTER) { MessageEnter(message); } if(message == cDef.MESSAGE_UPDATE) { MessageUpdate(message,keys); } if(message == cDef.MESSAGE_PAINT) { MessagePaint(message,pDC); } } error: warning C4832: token '.' is illegal after UDT 'cDef' see declaration of 'cDef' error C3861: 'MessageUpdate': identifier not found error C3861: 'MessageEnter': identifier not found error C3861: 'MessagePaint': identifier not found ..... Thanks in advance!

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  • Conversion between different template instantiation of the same template

    - by Naveen
    I am trying to write an operator which converts between the differnt types of the same implementation. This is the sample code: template <class T = int> class A { public: A() : m_a(0){} template <class U> operator A<U>() { A<U> u; u.m_a = m_a; return u; } private: int m_a; }; int main(void) { A<int> a; A<double> b = a; return 0; } However, it gives the following error for line u.m_a = m_a;. Error 2 error C2248: 'A::m_a' : cannot access private member declared in class 'A' d:\VC++\Vs8Console\Vs8Console\Vs8Console.cpp 30 Vs8Console I understand the error is because A<U> is a totally different type from A<T>. Is there any simple way of solving this (may be using a friend?) other than providing setter and getter methods? I am using Visual studio 2008 if it matters.

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  • Why is it that an int in C++ that isnt initialized (then used) doesn't return an error?

    - by omizzle
    I am new to C++ (just starting). I come from a Java background and I was trying out the following piece of code that would sum the numbers between 1 and 10 (inclusive) and then print out the sum: /* * File: main.cpp * Author: omarestrella * * Created on June 7, 2010, 8:02 PM */ #include <cstdlib> #include <iostream> using namespace std; int main() { int sum; for(int x = 1; x <= 10; x++) { sum += x; } cout << "The sum is: " << sum << endl; return 0; } When I ran it it kept printing 32822 for the sum. I knew the answer was supposed to be 55 and realized that its print the max value for a short (32767) plus 55. Changing int sum; to int sum = 0; would work (as it should, since the variable needs to be initialized!). Why does this behavior happen, though? Why doesnt the compiler warn you about something like this? I know Java screams at you when something isnt initialized. Thank you.

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  • Pointing class property to another class with vectors

    - by jmclem
    I've got a simple class, and another class that has a property that points to the first class: #include <iostream> #include <vector> using namespace std; class first{ public: int var1; }; class second{ public: first* classvar; }; Then, i've got a void that's supposed to point "classvar" to the intended iteration of the class "first". void fill(vector<second>& sec, vector<first>& fir){ sec[0].classvar = &fir[0]; } Finally the main(). Create and fill a vector of class "first", create "second" vector, and run the fill function. int main(){ vector<first> a(1); a[0].var1 = 1000; vector<second> b(1); fill(b, a); cout << b[0].classvar.var1 << '\n'; system("PAUSE"); return 0; } This gives me the following error: 1>c:\...\main.cpp(29) : error C2228: left of '.var1' must have class/struct/union 1> type is 'first *' And I can't figure out why it reads the "classvar" as the whole vector instead of just the single instance. Should I do this cout << b[0].classvar[0].var1 << '\n'; it reads perfectly. Can anyone figure out the problem? Thanks in advance

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  • Variable not accessible within an if statment

    - by Chris
    I have a variable which holds a score for a game. My variable is accessible and correct outside of an if statement but not inside as shown below score is declared at the top of the main.cpp and calculated in the display function which also contains the code below cout << score << endl; //works if(!justFinished){ cout << score << endl; // doesn't work prints a large negative number endTime = time(NULL); ifstream highscoreFile; highscoreFile.open("highscores.txt"); if(highscoreFile.good()){ highscoreFile.close(); }else{ std::ofstream outfile ("highscores.txt"); cout << score << endl; outfile << score << std::endl; outfile.close(); } justFinished = true; } cout << score << endl;//works

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  • c++ templates and inheritance

    - by Armen Ablak
    Hey, I'm experiencing some problems with breaking my code to reusable parts using templates and inheritance. I'd like to achieve that my tree class and avltree class use the same node class and that avltree class inherits some methods from the tree class and adds some specific ones. So I came up with the code below. Compiler throws an error in tree.h as marked below and I don't really know how to overcome this. Any help appreciated! :) node.h: #ifndef NODE_H #define NODE_H #include "tree.h" template <class T> class node { T data; ... node() ... friend class tree<T>; }; #endif tree.h #ifndef DREVO_H #define DREVO_H #include "node.h" template <class T> class tree { public: //signatures tree(); ... void insert(const T&); private: node<T> *root; //missing type specifier - int assumed. Note: C++ does not support default-int }; //implementations #endif avl.h #ifndef AVL_H #define AVL_H #include "tree.h" #include "node.h" template <class T> class avl: public tree<T> { public: //specific int findMin() const; ... protected: void rotateLeft(node<T> *)const; private: node<T> *root; }; #endif avl.cpp (I tried separating headers from implementation, it worked before I started to combine avl code with tree code) #include "drevo" #include "avl.h" #include "vozlisce.h" template class avl<int>; //I know that only avl with int can be used like this, but currently this is doesn't matter :) //implementations ...

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