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• Type problem when including tuple

  - by Person

  I'm using Visual Studio 2008 with Feature Pack 1. I have a typedef like this typedef std::tr1::tuple<std::string, std::string, int> tileInfo with a function like this const tileInfo& GetTile( int x, int y ) const. In the implementation file the function has the exact same signature (with the added class name qualifier) and I am getting a redefinition: different type modifiers error. It seems to be looking for an int& instead of a tileInfo& When I mouse over the type of the function in the header, i.e. tileInfo& it brings up a little bar saying static const int tileInfo. I think this may be the problem, but I'm not sure what to do. Any help is appreciated, thanks.

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• String Vector program exits before input

  - by kylepayne

  So, I have a project that must add, delete, and print the contents of a vector... the problem is that, when run the program exits before I can type in the string to add to the vector. I commented the function that that portion is in. Thanks! #include <iostream> #include <cstdlib> #include <vector> #include <string> using namespace std; void menu(); void addvector(vector<string>& vec); void subvector(vector<string>& vec); void vectorsize(const vector<string>& vec); void printvec(const vector<string>& vec); void printvec_bw(const vector<string>& vec); int main() { vector<string> svector; menu(); return 0; } //functions definitions void menu() { vector<string> svector; int choice = 0; cout << "Thanks for using this program! \n" << "Enter 1 to add a string to the vector \n" << "Enter 2 to remove the last string from the vector \n" << "Enter 3 to print the vector size \n" << "Enter 4 to print the contents of the vector \n" << "Enter 5 ----------------------------------- backwards \n" << "Enter 6 to end the program \n"; cin >> choice; switch(choice) { case 1: addvector(svector); break; case 2: subvector(svector); break; case 3: vectorsize(svector); break; case 4: printvec(svector); break; case 5: printvec_bw(svector); break; case 6: exit(1); default: cout << "not a valid choice \n"; // menu is structured so that all other functions are called from it. } } void addvector(vector<string>& vec) { string line; int i = 0; cout << "Enter the string please \n"; getline(cin, line); // doesn't prompt for input! vec.push_back(line); } void subvector(vector<string>& vec) { vec.pop_back(); return; } void vectorsize(const vector<string>& vec) { if (vec.empty()) { cout << "vector is empty"; } else { cout << vec.size() << endl; } return; } void printvec(const vector<string>& vec) { for(int i = 0; i < vec.size(); i++) { cout << vec[i] << endl; } return; } void printvec_bw(const vector<string>& vec) { for(int i = vec.size(); i > 0; i--) { cout << vec[i] << endl; } return; }

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• Beginner assembly programming memory usage question

  - by Daniel

  I've been getting into some assembly lately and its fun as it challenges everything i have learned. I was wondering if i could ask a few questions When running an executable, does the entire executable get loaded into memory? From a bit of fiddling i've found that constants aren't really constants? Is it just a compiler thing? const int i = 5; _asm { mov i, 0 } // i is now 0 and compiles fine So are all variables assigned with a constant value embedded into the file as well? Meaning: int a = 1; const int b = 2; void something() { const int c = 3; int d = 4; } Will i find all of these variables embedded in the file (in a hex editor or something)? If the executable is loaded into memory then "constants" are technically using memory? I've read around on the net people saying that constants don't use memory, is this true?

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• passing string literal to std::map::find(..)

  - by ra170

  I've got a std::map. I'm passing string literal to find method. Obviously, I can pass a string literal such as .find("blah"); However, I wanted to declare it upfront, instead of hardcoding the string, so I have couple of choices now: const std::string mystring = "blah"; const char mystring[] = "blah"; static const char * mystring = "blah"; They all work. (or at least compile). My question is, which one should I use? what's the advantage/distavantage over of the other?

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• C++'s std::string pools, debug builds? std::string and valgrind problems

  - by Den.Jekk

  Hello, I have a problem with many valgrind warnings about possible memory leaks in std::string, like this one: 120 bytes in 4 blocks are possibly lost in loss record 4,192 of 4,687 at 0x4A06819: operator new(unsigned long) (vg_replace_malloc.c:230) by 0x383B89B8B0: std::string::_Rep::_S_create(unsigned long, unsigned long, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.8) by 0x383B89C3B4: (within /usr/lib64/libstdc++.so.6.0.8) by 0x383B89C4A9: std::basic_string<char, std::char_traits<char>, std::allocator<char> >::basic_string(char const*, unsigned long, std::allocator<char> const&) (in /usr/lib64/libstdc++.so.6.0.8) I'm wondering: does std::string (GCC 4.1.2) use any memory pools? if so, is there any way to disable the pools (in form of a debug build etc.)? Regards, Den

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• Referenced vector does not pass through functions

  - by kylepayne

  The referenced vector to functions does not hold the information in memory. Do I have to use pointers? Thanks. #include <iostream> #include <cstdlib> #include <vector> #include <string> using namespace std; void menu(); void addvector(vector<string>& vec); void subvector(vector<string>& vec); void vectorsize(const vector<string>& vec); void printvec(const vector<string>& vec); void printvec_bw(const vector<string>& vec); int main() { vector<string> svector; menu(); return 0; } //functions definitions void menu() { vector<string> svector; int choice = 0; cout << "Thanks for using this program! \n" << "Enter 1 to add a string to the vector \n" << "Enter 2 to remove the last string from the vector \n" << "Enter 3 to print the vector size \n" << "Enter 4 to print the contents of the vector \n" << "Enter 5 ----------------------------------- backwards \n" << "Enter 6 to end the program \n"; cin >> choice; switch(choice) { case 1: addvector(svector); menu(); break; case 2: subvector(svector); menu(); break; case 3: vectorsize(svector); menu(); break; case 4: printvec(svector); menu(); break; case 5: printvec_bw(svector); menu(); break; case 6: exit(1); default: cout << "not a valid choice \n"; // menu is structured so that all other functions are called from it. } } void addvector(vector<string>& vec) { //string line; //int i = 0; //cin.ignore(1, '\n'); //cout << "Enter the string please \n"; //getline(cin, line); vec.push_back("the police man's beard is half-constructed"); } void subvector(vector<string>& vec) { vec.pop_back(); return; } void vectorsize(const vector<string>& vec) { if (vec.empty()) { cout << "vector is empty"; } else { cout << vec.size() << endl; } return; } void printvec(const vector<string>& vec) { for(int i = 0; i < vec.size(); i++) { cout << vec[i] << endl; } return; } void printvec_bw(const vector<string>& vec) { for(int i = vec.size(); i > 0; i--) { cout << vec[i] << endl; } return; }

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• Question regarding two dimensional array

  - by Sherwood Hu

  I have some problems using two dimensional array in the code and need some help. static const int PATTERNS[20][4]; static void init_PATTERN() { // problem #1 int (&patterns)[20][4] = const_cast<int[20][4]>(PATTERNS); ... } extern void UsePattern(int a, const int** patterns, int patterns_size); // problem #2 UsePattern(10, PATTERNS, sizeof(PATTERNS)/sizeof(PATTERNS[0])); in the first statement, I need to cast the const off the two dimensional array PATTERNS. The reason for this is that the init function is called only once, and in the remaining code, PATTERNS is strictly read-only. In the second statement, I need to pass PATTERNS array to the int** argument. Direct passing resulted a compile error. Thanks!

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• Template meta-programming with member function pointers?

  - by wheaties

  Is it possible to use member function pointers with template meta-programming? Such as: class Connection{ public: string getName() const; string getAlias() const; //more stuff }; typedef string (Connection::*Con_Func)() const; template<Con_Func _Name> class Foo{ Connection m_Connect; public: void Foo(){ cout << m_Connect.(*_Name); } }; typedef Foo<&Connection::getName> NamedFoo; typedef Foo<&Connection::getAlias> AliasFoo; Granted, this is rather contrived but is it possible? (yes, there are probably much better ways but humor me.)

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• Php code not executing - dies out when trying to refer to member of static class - no error displaye

  - by Ali

  I'm having some problems with this piece of code. I've included a class declaration and trying to create an object of that class but my code dies out. It doesn't seem to be an include issue as all the files are being included even the files called for inclusion within the class file itself. However the object is not created - I tried to put an echo statement in the __construct function but nothing it just doesn't run infact doesn't create the object and the code won't continue from there - plus no error is reported or displayed and I have error reporting set to E_ALL and display errors set to true WHats happening here :( =============EDIT SOrry I checked again the error is prior to teh object creation thing - it dies out when it tries to refer to a constant in a static class like so: $v = Zend_Oauth::REQUEST_SCHEME_HEADER; THis is the class or part of it - it has largely static functions its the Zend Oauth class: class Zend_Oauth { const REQUEST_SCHEME_HEADER = 'header'; const REQUEST_SCHEME_POSTBODY = 'postbody'; const REQUEST_SCHEME_QUERYSTRING = 'querystring'; // continued LIke I said no error is being reported at all :(

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• C errors - Cannot combine with previous 'struct' declaration specifier && Redefinition of 'MyMIDINotifyProc' as different kind of symbol

  - by user1905634

  I'm still new to C but trying to understand it better by working my way through a small MIDI audio unit (in Xcode 4.3.3). I've been searching for an answer to this all day and still don't even understand exactly what the problem is. Here's the code in question: //MyMIDINotifyProc.h #ifndef MIDIInstrumentUnit_CallbackProcs_h #define MIDIInstrumentUnit_CallbackProcs_h void MyMIDINotifyProc (const MIDINotification *message, void *refCon); #endif //MyMIDINotifyProc.c #include <CoreMIDI/CoreMIDI.h> #include "MyMIDINotifyProc.h" void MyMIDINotifyProc (const MIDINotification *message, void *refCon) { //manage notification } In the header definition I get this: ! Cannot combine with previous 'struct' declaration specifier I've made sure the definitions match and tried renaming them and I still get this in my .c file: ! Redefinition of 'MyMIDINotifyProc' as different kind of symbol Which points to the .h definition as the 'Previous definition'. I know that MIDIServices.h in the CoreMIDI framework defines: typedef void (*MIDINotifyProc)(const MIDINotification *message, void *refCon); But I don't understand if/why that would cause an error. I would be grateful if anyone could offer some help.

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• Pointer to a C++ class member function as a global function's parameter?

  - by marcin1400

  I have got a problem with calling a global function, which takes a pointer to a function as a parameter. Here is the declaration of the global function: int lmdif ( minpack_func_mn fcn, void *p, int m, int n, double *x, double *fvec, double ftol) The "minpack_func_mn" symbol is a typedef for a pointer to a function, defined as: typedef int (*minpack_func_mn)(void *p, int m, int n, const double *x, double *fvec, int iflag ); I want to call the "lmdif" function with a pointer to a function which is a member of a class I created, and here is the declaration of this class function: int LT_Calibrator::fcn(void *p, int m, int n, const double *x, double *fvec,int iflag) I am calling a global function like this: info=lmdif(&LT_Calibrator::fcn, 0, m, n, x, fvec, ftol) Unfortunately, I get a compiler error, which says: "error C2664: 'lmdif' : cannot convert parameter 1 from 'int (__thiscall LT_Calibrator::* )(void *,int,int,const double *,double *,int)' to 'minpack_func_mn' 1 There is no context in which this conversion is possible" Is there any way to solve that problem?

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• C++ Why is the copy constructor implicitly called?

  - by ShaChris23

  Why is the Child class's copy constructor called in the code below? I mean, it automatically converts Base to Child via the Child copy constructor. The code below compiles, but shouldn't it not compile since I haven't provided bool Child::operator!=(Base const&)? class Base { }; class Child : public Base { public: Child() {} Child(Base const& base_) : Base(base_) { std::cout <<"should never called!"; } bool operator!=(Child const&) { return true; } }; void main() { Base base; Child child; if(child != base) std::cout << "not equal"; else std::cout << "equal"; }

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• C++: conjunction of binds?

  - by Helltone

  Suppose the following two functions: #include <iostream> #include <cstdlib> // atoi #include <cstring> // strcmp #include <boost/bind.hpp> bool match1(const char* a, const char* b) { return (strcmp(a, b) == 0); } bool match2(int a, const char* b) { return (atoi(b) == a); } Each of these functions takes two arguments, but can be transformed into a callable object that takes only one argument by using (std/boost)bind. Something along the lines of: boost::bind(match1, "a test"); boost::bind(match2, 42); I want to be able to obtain, from two functions like these that take one argument and return bool, a callable object that takes two arguments and returns the && of the bools. The type of the arguments is arbitrary. Something like an operator&& for functions that return bool.

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• Problem accessing base member in derived constructor

  - by LeopardSkinPillBoxHat

  Given the following classes: class Foo { struct BarBC { protected: BarBC(uint32_t aKey) : mKey(aKey) mOtherKey(0) public: const uint32_t mKey; const uint32_t mOtherKey; }; struct Bar : public BarBC { Bar(uint32_t aKey, uint32_t aOtherKey) : BarBC(aKey), mOtherKey(aOtherKey) // Compile error here }; }; I am getting a compilation error at the point indicated: error: class `Foo::Bar' does not have any field named `mOtherKey'. Can anyone explain this? I suspect it's a syntactical problem due to my Bar class being defined within the Foo class, but can't seem to find a way around it. This is simple public inheritance, so mOtherKey should be accessible from the Bar constructor. Right? Or is it something to do with the fact that mOtherKey is const and I have already initialised it to 0 in the BarBC constructor?

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• question about c++ template functions taking any type as long that type meets at least one of the re

  - by smerlin

  Since i cant explain this very well, i will start with a small example right away: template <class T> void Print(const T& t){t.print1();} template <class T> void Print(const T& t){t.print2();} This does not compile: error C2995: 'void Print(const T &)' : function template has already been defined So, how can i create a template function which takes any type T as long as that type has a print1 memberfunction OR a print2 memberfunction (no polymorphism) ?

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• Lifetime of implicitly casted temporaries

  - by Answeror

  I have seen this question. It seems that regardless of the cast, the temporary object(s) will "survive" until the fullexpression evaluated. But in the following scenario: void foo(boost::tuple<const double&> n) { printf("%lf\n", n.get<0>()); } int main() { foo(boost::tuple<const double&>(2));//#1 foo(boost::make_tuple(2));//#2 return 0; } 1 run well, but 2 do not. And MSVC gave me a warning about 2: "reference member is initialized to a temporary that doesn't persist after the constructor exits" Now I am wondering why they both make a temporary "double" object and pass it to boost::tuple<const double&> and only 2 failed.

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• C++ Segmentation fault in binary_function

  - by noryb009

  I'm using Visual Studio 2010 Beta 2 (also tried with NetBeans), and I'm having a segmentation fault in the following code: // One of the @link s20_3_3_comparisons comparison functors@endlink. template <class _Tp> struct less : public binary_function<_Tp, _Tp, bool> { bool operator()(const _Tp& __x, const _Tp& __y) const { return __x < __y; } //this is the problem line }; I don't know what in my program calls it, but I am trying to find out. (I think it's a map) Does anyone know what to do, or has encountered this before?

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• C++: Define simple string?

  - by Jason

  This thing is really wracking my mind. I'm learning C++ and I wanted to define a constant that I can use in another function, A short answer on how to do this will be fine.. Lets say at the beginning of my code I want to define this constant: //After #includes bool OS = 1; //1 = linux if (OS) { const ??? = "clear"; } else { const ??? = "cls"; } I don't know what type to use to define the "clear" string... I'm so confused. Later on I want to use it within a function: int foo() { system(::cls); //:: for global return 0; } How would I define the string up top, and use the string down below? I heard char only had one character and things... I'm not sure how to use , since it says it's converting string into const char or something.

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• How do I create a set with std::pair thats sorted based on the ::second pair member using bind

  - by Stone Free

  I know I could use the following: template <typename Pair> struct ComparePairThroughSecond : public std::unary_function<Pair, bool> { bool operator ()(const Pair& p1, const Pair& p2) const { return p1.second < p2.second; } }; std::set<std::pair<int, long>, ComparePairThroughSecond> somevar; but wondered if it could be done with boost::bind

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• non-scalar type requested

  - by lego69

  can somebody please help me with an error conversion from `A' to non-scalar type `B' requested I have class A and derived from it B, but I have problems with these rows: A a(1); A *pb = new B(a); B b = *pb; //here I have an error thanks in advance for any help class A { protected: int player; public: A(int initPlayer = 0); A(const A&); A& operator=(const A&); virtual ~A(){}; virtual void foo(); void foo() const; operator int(); }; class B: public A { public: B(int initPlayer): A(initPlayer){}; ~B(){}; virtual void foo(); };

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• C++ Segementation fault in binary_function

  - by noryb009

  I'm using Visual Studio 2010 Beta 2 (also tried with NetBeans), and I'm having a segmentation fault in the following code: // One of the @link s20_3_3_comparisons comparison functors@endlink. template <class _Tp> struct less : public binary_function<_Tp, _Tp, bool> { bool operator()(const _Tp& __x, const _Tp& __y) const { return __x < __y; } //this is the problem line }; I don't know what in my program calls it, but I am trying to find out. (I think it's a map) Does anyone know what to do, or has encountered this before?

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• c++: strange syntax in what() method of std::exception

  - by Patrick Oscity

  When i am inheriting from std::exception in order to define my own exception type, i need to override the what() method, which has the following signature: virtual const char* what() const throw(); This definitely looks strange to me, like if there were two method names in the signature. Is this some very specific syntax, like with pure virtual methods, e.g.: virtual int method() const = 0; or is this a feature, that could somehow be used in another context, too? And if so, for what could it be used?

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• `.' cannot appear in a constant-expression

  - by Amir Rachum

  Hi all, I'm getting the following error: `.' cannot appear in a constant-expression for this function (line 4): bool Covers(const Region<C,V,D>& other) const { const Region& me = *this; for (unsigned d = 0; d < D; d++) { if (me[d].min > other[d].min || me[d].max < other[d].max) { return false; } } can anyone explain the problem please?

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• Getting count() of class static array

  - by xylar

  Is it possible to get the count of a class defined static array? For example: class Model_Example { const VALUE_1 = 1; const VALUE_2 = 2; const VALUE_3 = 3; public static $value_array = array( self::VALUE_1 => 'boing', self::VALUE_2 => 'boingboing', self::VALUE_3 => 'boingboingboing', ); public function countit() { // count number $total = count(self::$value_array ); echo ': '; die($total); } } At the moment calling the countit() method returns :

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• Click a button in another application

  - by sam

  I want yo use SendMessage or PostMessage to press a button in another app i have a sample code to do this but by getting Window Handle, but don't work also i used "WinDowse" to get required info. here is the code private const uint BM_CLICK = 0x00F5; private const uint WM_LBUTTONDOWN = 0x0201; private const uint WM_LBUTTONUP = 0x0202; private void PushOKButton(IntPtr ptrWindow) { WindowHandle = FindWindow(null, "Form1"); if (ptrWindow == IntPtr.Zero) return; IntPtr ptrOKButton = FindWindowEx(ptrWindow, IntPtr.Zero, "Button", "&Yes"); if (ptrOKButton == IntPtr.Zero) return; SendMessage(ptrOKButton, WM_LBUTTONDOWN, 0, 0); SendMessage(ptrOKButton, WM_LBUTTONUP, 0, 0); SendMessage(ptrOKButton, BM_CLICK, 0, 0); } is There a Compelete Suloution in c# ?

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