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  • Which namespace does operator<< (stream) go to?

    - by aaa
    If I have have some overloaded ostream operators, defined for library local objects, is its okay for them to go to std namespace? If I do not declare them in std namespace, then I must use using ns:: operator <<. As a possible follow-up question, are there any operators which should go to standard or global namespace?

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  • How to pass operators as parameters

    - by Rodion Ingles
    I have to load an array of doubles from a file, multiply each element by a value in a table (different values for different elements), do some work on it, invert the multiplication (that is, divide) and then save the data back to file. Currently I implement the multiplication and division process in two separate methods. Now there is some extra work behind the scenes but apart from the specific statements where the multiplication/division occurs, the rest of the code is identical. As you can imagine, with this approach you have to be very careful making any changes. The surrounding code is not trivial, so its either a case of manually editing each method or copying changes from one method to the other and remembering to change the * and / operators. After too many close calls I am fed up of this and would like to make a common function which implements the common logic and two wrapper functions which pass which operator to use as a parameter. My initial approach was to use function pointers: MultiplyData(double data) { TransformData(data, &(operator *)); } DivideData(double data) { TransformData(data, &(operator /)); } TransformData(double data, double (*func)(double op1, double op2)) { /* Do stuff here... */ } However, I can't pass the operators as pointers (is this because it is an operator on a native type?), so I tried to use function objects. Initially I thought that multiplies and divides functors in <functional> would be ideal: MultiplyData(double data) { std::multiplies<double> multFunct; TransformData(data, &multFunct); } DivideData(double data) { std::divides<double> divFunct; TransformData(data, &divFunct); } TransformData(double data, std::binary_function<double, double, double> *funct) { /* Do stuff here... */ } As you can see I was trying to use a base class pointer to pass the functor polymorphically. The problem is that std::binary_function does not declare an operator() member for the child classes to implement. Is there something I am missing, or is the solution to implement my own functor heirarchy (which really seems more trouble than it is worth)?

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  • async_write/async_read problems while trying to implement question-answer logic

    - by Max
    Good day. I'm trying to implement a question - answer logic using boost::asio. On the Client I have: void Send_Message() { .... boost::asio::async_write(server_socket, boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Client::Handle_Write_Message, this, boost::asio::placeholders::error)); .... } void Handle_Write_Message(const boost::system::error_code& error) { .... std::cout << "Message was sent.\n"; .... boost::asio::async_read(server_socket_,boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Client::Handle_Read_Message, this, boost::asio::placeholders::error)); .... } void Handle_Read_Message(const boost::system::error_code& error) { .... std::cout << "I have a new message.\n"; .... } And on the Server i have the "same - logic" code: void Read_Message() { .... boost::asio::async_read(client_socket, boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Server::Handle_Read_Message, this, boost::asio::placeholders::error)); .... } void Handle_Read_Message(const boost::system::error_code& error) { .... std::cout << "I have a new message.\n"; .... boost::asio::async_write(client_socket_,boost::asio::buffer(&Message, sizeof(Message)), boost::bind(&Server::Handle_Write_Message, this, boost::asio::placeholders::error)); .... } void Handle_Write_Message(const boost::system::error_code& error) { .... std::cout << "Message was sent back.\n"; .... } Message it's just a structure. And the output on the Client is: Message was sent. Output on the Server is: I have a new message. And that's all. After this both programs are still working but nothing happens. I tried to implement code like: if (!error) { .... } else { // close sockets and etc. } But there are no errors in reading or writing. Both programs are just running normally, but doesn't interact with each other. This code is quite obvious but i can't understand why it's not working. Thanks in advance for any advice.

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  • Regular expressions in c++ STL

    - by Radek Šimko
    Is there any native library in STL which is tested and works without any extra compiler options? I tried to use <regex>, but the compiler outputs this: In file included from /usr/include/c++/4.3/regex:40, from main.cpp:5: /usr/include/c++/4.3/c++0x_warning.h:36:2: error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options.

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  • include and using namespace in C++

    - by cambr
    for using cout, I need to specify both: #include<iostream> and using namespace std; Where is cout defined? in iostream, correct? So, it is that iostream itself is there in namespace std? What is the meaning of both the statements with respect to using cout? I am confused why we need to include them both.

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  • Sprite not moving when using a function from another class SFML c++

    - by user2892932
    I have a Game.cpp, and I am calling a update function in my Player class. In my player update Function I have it to check for keyboard input, and it seems to work, but whenever I try to call the .move() function, it seems to not work. I get no errors either. I am new to sfml, and decent with c++. Help is appreciated! #include "Player.h" Player::Player(void): vel(0), maxvel(100) { Load("Assets/sss.png",true); } void Player::Update(sf::Sprite& p) { if (sf::Keyboard::isKeyPressed(sf::Keyboard::A)) { moveObject(-3,0, p); } if(sf::Keyboard::isKeyPressed(sf::Keyboard::D)) { moveObject(-3,0, p); } } Player::~Player(void) { } This is the GameObject cpp #include "GameObject.h" #include <iostream> GameObject::GameObject(void) { isLoaded = false; } void GameObject::Load(std::string flname, bool isPlayer) { if(!tex.loadFromFile(flname)) { EXIT_FAILURE; } else { if(isPlayer) { if(!tex.loadFromFile(flname, sf::IntRect(0,0,33,33))) { EXIT_FAILURE; } else { std::cout << "Loading image" << "\n"; filename = flname; spr.setTexture(tex); isLoaded = true; } } else { std::cout << "Loading image" << "\n"; filename = flname; spr.setTexture(tex); isLoaded = true; } } } void GameObject::Draw(sf::RenderWindow & window) { if(isLoaded) { window.draw(spr); window.display(); std::cout << "Sprite drew" << "\n"; } } void GameObject::setPos(float x, float y) { if(isLoaded) { spr.setPosition(x,y); } } sf::Vector2f GameObject::GetObjPos() { return spr.getPosition(); } sf::Sprite& GameObject::getSprite() { return spr; } void GameObject::moveObject(float x, float y, sf::Sprite& sp) { sp.move(x, y); } GameObject::~GameObject(void) { }

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  • Function templates for arbitrary STL containers containing arbitrary types.

    - by Chad Brewbaker
    I have an arbitrary STL container C, which contains elements of an arbitrary type T. I want to create an std::vector that has a copy of all the elements. What is the cleanest way to do this? template <typename C> void myfunction(C container){ /*Derive the type T of elements within the container*/ std::vector<T> mystack; /* Iterate over container and push_back() the elements into mystack*/ }

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  • boost::regex_replace() replaces only first occurrence, why?

    - by Vincenzo
    My code: #include <string> #include <boost/algorithm/string/regex.hpp> std::cout << boost::algorithm::replace_regex_copy( "{x}{y}", // source string boost::regex("\\{.*?\\}"), // what to find std::string("{...}") // what to replace to ); This is what I see: {…}{y} Thus, only the first occurrence replaced. Why? How to solve it?

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  • Attempt to open browser in C++

    - by Machiel
    Hey there, I am attempting to open Firefox using C++ on Linux (Ubuntu). However, I get an segmentation fault. What am I doing wrong, and what should I do? std::cout << system("/usr/bin/firefox") << std::endl; I hope to hear from you. Kind regards, Machiel

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  • How can I get the same strstream functionality now that's deprecated?

    - by chila
    I use to write code like this: void fun(char *buff, unsigned size) { std::strstream str(buff, size); str << "hello world: " << 5; } so I can use stream output over an arbitrary buffer. I've found this technique both efficient (no allocations) and useful (streams!). Now that std::strstream is deprecated, how can I get the same speed+flexibility that I can get with this code?

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  • Best way to have common class shared by both C++ and Ruby?

    - by shuttle87
    I am currently working on a project where a team of us are designing a game, all of us are proficient in ruby and some (but not all) of us are proficient in c++. Initially we made the backend in ruby but we ported it to c++ for more speed. The c++ port of the backend has exactly the same features and algorithms as the original ruby code. However we still have a bunch of code in ruby that does useful things but we want it to now get the data from the c++ classes. Our first thought was that we could save some of the data structures in something like XML or redis and call that, but some of the developers don't like that idea. We don't need anything particularly complex data structures to be passed between the different parts of the code, just tuples, strings and ints. Is there any way of integrating the ruby code so that it can call the c++ stuff natively? Will we need to embed code? Will we have to make a ruby extension? If so are there any good resources/tutorials you could suggest? For example say we have this code in the c++ backend: class The_game{ private: bool printinfo; //print the player diagnostic info at the beginning if true int numplayers; std::vector<Player*> players; string current_action; int action_is_on; // the index of the player in the players array that the action is now on //more code here public: Table(std::vector<Player *> in_players, std::vector<Statistics *> player_stats ,const int in_numplayers); ~Table(); void play_game(); History actions_history; }; class History{ private: int action_sequence_number; std::vector<Action*> hand_actions; public: void print_history(); void add_action(Action* the_action_to_be_added); int get_action_sequence_number(){ return action_sequence_number;} bool history_actions_are_equal(); int last_action_size(int street,int number_of_actions_ago); History(); ~History(); }; Is there any way to natively call something in the actions_history via The_game object in ruby? (The objects in the original ruby code all had the same names and functionality) By this I mean: class MyRubyClass def method1(arg1) puts arg1 self.f() # ... but still available puts cpp_method.the_current_game.actions_history.get_action_sequence_number() end # Constructor: def initialize(arg) puts "In constructor with arg #{arg}" #get the c++ object here and call it cpp_method end end Is this possible? Any advice or suggestions are appreciated.

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  • C++ stream as a parameter when overloading operator<<

    - by TheOm3ga
    I'm trying to write my own logging class and use it as a stream: logger L; L << "whatever" << std::endl; This is the code I started with: #include <iostream> using namespace std; class logger{ public: template <typename T> friend logger& operator <<(logger& log, const T& value); }; template <typename T> logger& operator <<(logger& log, T const & value) { // Here I'd output the values to a file and stdout, etc. cout << value; return log; } int main(int argc, char *argv[]) { logger L; L << "hello" << '\n' ; // This works L << "bye" << "alo" << endl; // This doesn't work return 0; } But I was getting an error when trying to compile, saying that there was no definition for operator<<: pruebaLog.cpp:31: error: no match for ‘operator<<’ in ‘operator<< [with T = char [4]](((logger&)((logger*)operator<< [with T = char [4]](((logger&)(& L)), ((const char (&)[4])"bye")))), ((const char (&)[4])"alo")) << std::endl’ So, I've been trying to overload operator<< to accept this kind of streams, but it's driving me mad. I don't know how to do it. I've been loking at, for instance, the definition of std::endl at the ostream header file and written a function with this header: logger& operator <<(logger& log, const basic_ostream<char,char_traits<char> >& (*s)(basic_ostream<char,char_traits<char> >&)) But no luck. I've tried the same using templates instead of directly using char, and also tried simply using "const ostream& os", and nothing. Another thing that bugs me is that, in the error output, the first argument for operator<< changes, sometimes it's a reference to a pointer, sometimes looks like a double reference...

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  • Can AutoCAD entities be serialized?

    - by billmuell
    Using ObjectARX (C++) for AutoCAD 2010, can AutoCAD entities be serialized? We need to save the serialized entity in a field in a database (Oracle, PostgreSQL, etc., not AcDbDatabase). It'OK if you show me how to save them in disk, something like this: AcDbEntity * entity; ... std::ofstream ofs("c:\\filename.fil", std::ios::binary); ofs.write((char *)(entity), sizeof(entity)); ofs.close(); Thanks

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  • Binary Search Tree Contains Function

    - by Suede
    I am trying to write a "contains" function for a binary search tree. I receive the following error at compile "Unhandled exception at 0x77291CB3 (ntdll.dll) in BST.exe: 0xC00000FD: Stack overflow (parameters: 0x00000001, 0x001E2FFC)." The following is my code. struct Node { int data; Node* leftChild; Node* rightChild; Node() : leftChild(NULL), rightChild(NULL) {} }; struct BST { Node* root; BST() : root(NULL) {} void insert(int value); bool contains(int value); }; void BST::insert(int value) { Node* temp = new Node(); temp->data = value; if(root == NULL) { root = temp; return; } Node* current; current = root; Node* parent; parent = root; current = (temp->data < current->data ? (current->leftChild) : (current->rightChild) while(current != NULL) { parent = current; current = (temp->data < current->data) ? (current->leftChild) : (current->rightChild) } if(temp->data < parent->data) { parent->leftChild = temp; } if(temp->data > parent->data) { parent->rightChild = temp; } } bool BST::contains(int value) { Node* temp = new Node(); temp->data = value; Node* current; current = root; if(temp->data == current->data) { // base case for when node with value is found std::cout << "true" << std::endl; return true; } if(current == NULL) { // base case if BST is empty or if a leaf is reached before value is found std::cout << "false" << std::endl; return false; } else { // recursive step current = (temp->data < current->data) ? (current->leftChild) : (current->rightChild); return contains(temp->data); } } int main() { BST bst; bst.insert(5); bst.contains(4); system("pause"); } As it stands, I would insert a single node with value '5' and I would search the binary search tree for a node with value '4' - thus, I would expect the result to be false.

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  • Why does string::find return size_type and not an iterator?

    - by dehmann
    In C++, why does string::find return size_type and not an iterator? It would make sense because functions like string::replace or string::insert take iterators as input, so you could find some character and immediately pass the returned iterator to replace, etc. Also, std::find returns an iterator -- why is std::string::find different?

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  • C++, class as parameter to a method, not template.

    - by ra170
    So, I came across an interesting method signature that I don't quite understand, it went along the lines of: void Initialize(std::vector< std::string > & param1, class SomeClassName * p); what I don't understand is the "class" keyword being used as the parameter, why is it there? Is it necessary to specify or it is purely superficial?

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  • How can I have a Foo* iterator to a vector of Foo?

    - by mghie
    If I have a class that contains a std::list<Foo>, how can I implement iterators to a Foo* collection, preferably without using boost? I'd rather not maintain a parallel collection of pointers. For now I have std::list<Foo>, mostly so that removing or inserting an element does not invalidate all other iterators, but would it be possible to implement other iterators too, so that the collection type used in the implementation is opaque to the user of the class?

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