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• Can't compile std::map sorting, why?

  - by Vincenzo

  This is my code: map<string, int> errs; struct Compare { bool operator() (map<string, int>::const_iterator l, map<string, int>::const_iterator r) { return ((*l).second < (*r).second); } } comp; sort(errs.begin(), errs.end(), comp); Can't compile. This is what I'm getting: no matching function for call to ‘sort(..’ Why so? Can anyone help? Thanks!

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• using std::freopen to redirect stderr c++

  - by chriscisco

  So I want to redirect all stderr to a file, which is also being used by my logger for the entire time the application (game) is running. The follow redirect it away from the console, but it never appears in my file, and using fclose after the game loop is over doesnt actually do anything, where it would normally would. freopen(Logger::logFile.c_str(),"a",stderr); Any help would be great on how to get stderr to output to the text file, in a game loop.

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• How can I read from an std::istream (using operator>>)?

  - by dehmann

  How can I read from an std::istream using operator>>? I tried the following: void foo(const std::istream& in) { std::string tmp; while(in >> tmp) { std::cout << tmp; } } But it gives an error: error: no match for 'operator>>' in 'in >> tmp'

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• deleting element objects of a std vector using erase : a) memory handling and b) better way?

  - by memC

  hi, I have a vec_A that stores instances of class A as: vec_A.push_back(A()); I want to remove some elements in the vector at a later stage and have two questions: a) The element is deleted as: vec_A.erase(iterator) Is there any additional code I need to add to make sure that there is no memory leak? . b) Assume that condition if(num <5) is if num is among a specific numberList. Given this, is there a better way to delete the elements of a vector than what I am illustrating below? #include<vector> #include<stdio.h> #include<iostream> class A { public: int getNumber(); A(int val); ~A(){}; private: int num; }; A::A(int val){ num = val; }; int A::getNumber(){ return num; }; int main(){ int i =0; int num; std::vector<A> vec_A; std::vector<A>::iterator iter; for ( i = 0; i < 10; i++){ vec_A.push_back(A(i)); } iter = vec_A.begin(); while(iter != vec_A.end()){ std::cout << "\n --------------------------"; std::cout << "\n Size before erase =" << vec_A.size(); num = iter->getNumber() ; std::cout << "\n num = "<<num; if (num < 5){ vec_A.erase(iter); } else{ iter++; } std::cout << "\n size after erase =" << vec_A.size(); } std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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• are C functions declared in <c____> headers guaranteed to be in the global namespace as well as std?

  - by Evan Teran

  So this is something that I've always wondered but was never quite sure about. So it is strictly a matter of curiosity, not a real problem. As far as I understand, what you do something like #include <cstdlib> everything (except macros of course) are declared in the std:: namespace. Every implementation that I've ever seen does this by doing something like the following: #include <stdlib.h> namespace std { using ::abort; // etc.... } Which of course has the effect of things being in both the global namespace and std. Is this behavior guaranteed? Or is it possible that an implementation could put these things in std but not in the global namespace? The only way I can think of to do that would be to have your libstdc++ implement every c function itself placing them in std directly instead of just including the existing libc headers (because there is no mechanism to remove something from a namespace). Which is of course a lot of effort with little to no benefit. The essence of my question is, is the following program strictly conforming and guaranteed to work? #include <cstdio> int main() { ::printf("hello world\n"); } EDIT: The closest I've found is this (17.4.1.2p4): Except as noted in clauses 18 through 27, the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in ISO/IEC 9899:1990 Programming Languages C (Clause 7), or ISO/IEC:1990 Programming Languages—C AMENDMENT 1: C Integrity, (Clause 7), as appropriate, as if by inclusion. In the C + + Standard Library, however, the declarations and definitions (except for names which are defined as macros in C) are within namespace scope (3.3.5) of the namespace std. which to be honest I could interpret either way. "the contents of each header cname shall be the same as that of the corresponding header name.h, as specified in ISO/IEC 9899:1990 Programming Languages C" tells me that they may be required in the global namespace, but "In the C + + Standard Library, however, the declarations and definitions (except for names which are defined as macros in C) are within namespace scope (3.3.5) of the namespace std." says they are in std (but doesn't specify any other scoped they are in).

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• Is valgrind crazy or is this is a genuine std map iterator memory leak?

  - by Alberto Toglia

  Well, I'm very new to Valgrind and memory leak profilers in general. And I must say it is a bit scary when you start using them cause you can't stop wondering how many leaks you might have left unsolved before! To the point, as I'm not an experienced in c++ programmer, I would like to check if this is certainly a memory leak or is it that Valgrind is doing a false positive? typedef std::vector<int> Vector; typedef std::vector<Vector> VectorVector; typedef std::map<std::string, Vector*> MapVector; typedef std::pair<std::string, Vector*> PairVector; typedef std::map<std::string, Vector*>::iterator IteratorVector; VectorVector vv; MapVector m1; MapVector m2; vv.push_back(Vector()); m1.insert(PairVector("one", &vv.back())); vv.push_back(Vector()); m2.insert(PairVector("two", &vv.back())); IteratorVector i = m1.find("one"); i->second->push_back(10); m2.insert(PairVector("one", i->second)); m2.clear(); m1.clear(); vv.clear(); Why is that? Shouldn't the clear command call the destructor of every object and every vector? Now after doing some tests I found different solutions to the leak: 1) Deleting the line i-second-push_back(10); 2) adding a delete i-second; after it's been used. 3) Deleting the second vv.push_back(Vector()); and m2.insert(PairVector("two", &vv.back())); statements. Using solution 2) makes Valgring print: 10 allocs, 11 frees Is that OK? As I'm not using new why should I delete? Thanks, for any help!

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• concurrency::accelerator

  - by Daniel Moth

  Overview An accelerator represents a "target" on which C++ AMP code can execute and where data can reside. Typically (but not necessarily) an accelerator is a GPU device. Accelerators are represented in C++ AMP as objects of the accelerator class. For many scenarios, you do not need to obtain an accelerator object, since the runtime has a notion of a default accelerator, which is what it thinks is the best one in the system. Examples where you need to deal with accelerator objects are if you need to pick your own accelerator (based on your specific criteria), or if you need to use more than one accelerators from your app. Construction and operator usage You can query and obtain a std::vector of all the accelerators on your system, which the runtime discovers on startup. Beyond enumerating accelerators, you can also create one directly by passing to the constructor a system-wide unique path to a device if you know it (i.e. the “Device Instance Path” property for the device in Device Manager), e.g. accelerator acc(L"PCI\\VEN_1002&DEV_6898&SUBSYS_0B001002etc"); There are some predefined strings (for predefined accelerators) that you can pass to the accelerator constructor (and there are corresponding constants for those on the accelerator class itself, so you don’t have to hardcode them every time). Examples are the following: accelerator::default_accelerator represents the default accelerator that the C++ AMP runtime picks for you if you don’t pick one (the heuristics of how it picks one will be covered in a future post). Example: accelerator acc; accelerator::direct3d_ref represents the reference rasterizer emulator that simulates a direct3d device on the CPU (in a very slow manner). This emulator is available on systems with Visual Studio installed and is useful for debugging. More on debugging in general in future posts. Example: accelerator acc(accelerator::direct3d_ref); accelerator::direct3d_warp represents a target that I will cover in future blog posts. Example: accelerator acc(accelerator::direct3d_warp); accelerator::cpu_accelerator represents the CPU. In this first release the only use of this accelerator is for using the staging arrays technique that I'll cover separately. Example: accelerator acc(accelerator::cpu_accelerator); You can also create an accelerator by shallow copying another accelerator instance (via the corresponding constructor) or simply assigning it to another accelerator instance (via the operator overloading of =). Speaking of operator overloading, you can also compare (for equality and inequality) two accelerator objects between them to determine if they refer to the same underlying device. Querying accelerator characteristics Given an accelerator object, you can access its description, version, device path, size of dedicated memory in KB, whether it is some kind of emulator, whether it has a display attached, whether it supports double precision, and whether it was created with the debugging layer enabled for extensive error reporting. Below is example code that accesses some of the properties; in your real code you'd probably be checking one or more of them in order to pick an accelerator (or check that the default one is good enough for your specific workload): void inspect_accelerator(concurrency::accelerator acc) { std::wcout << "New accelerator: " << acc.description << std::endl; std::wcout << "is_debug = " << acc.is_debug << std::endl; std::wcout << "is_emulated = " << acc.is_emulated << std::endl; std::wcout << "dedicated_memory = " << acc.dedicated_memory << std::endl; std::wcout << "device_path = " << acc.device_path << std::endl; std::wcout << "has_display = " << acc.has_display << std::endl; std::wcout << "version = " << (acc.version >> 16) << '.' << (acc.version & 0xFFFF) << std::endl; } accelerator_view In my next blog post I'll cover a related class: accelerator_view. Suffice to say here that each accelerator may have from 1..n related accelerator_view objects. You can get the accelerator_view from an accelerator via the default_view property, or create new ones by invoking the create_view method that creates an accelerator_view object for you (by also accepting a queuing_mode enum value of deferred or immediate that we'll also explore in the next blog post). Comments about this post by Daniel Moth welcome at the original blog.

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• How can I store spell & items using a std::vector implementation?

  - by Vladimir Marenus

  I'm following along with a book from GameInstitute right now, and it's asking me to: Allow the player to buy and carry healing potions and potions of fireball. You can add an Item array (after you define the item class) to the Player class for storing them, or use a std::vector to store them. I think I would like to use the std::vector implementation, because that seems to confuse me less than making an item class, but I am unsure how to do so. I've heard from many people that vectors are great ways to store dynamic values (such as items, weapons, etc), but I've not seen it used.

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• GNU C++ how to check when -std=c++0x is in effect?

  - by TerryP

  My system compiler (gcc42) works fine with the TR1 features that I want, but trying to support newer compiler versions other than the systems, trying to accessing TR1 headers an #error demanding the -std=c++0x option because of how it interfaces with library or some hub bub like that. /usr/local/lib/gcc45/include/c++/bits/c++0x_warning.h:31:2: 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. Having to supply an extra switch is no problem, to support GCC 4.4 and 4.5 under this system (FreeBSD), but obviously it changes the picture! Using my system compiler (g++ 4.2 default dialect): #include <tr1/foo> using std::tr1::foo; Using newer (4.5) versions of the compiler with -std=c++0x: #include <foo> using std::foo; Is there anyway using the pre processor, that I can tell if g++ is running with C++0x features enabled? Something like this is what I'm looking for: #ifdef __CXX0X_MODE__ #endif but I have not found anything in the manual or off the web. At this rate, I'm starting to think that life would just be easier, to use Boost as a dependency, and not worry about a new language standard arriving before TR4... hehe.

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• vector iterator not dereferencable at runtime on a vector<vector<vector<A*>*>*>

  - by marouanebj

  Hi, I have this destructor that create error at runtime "vector iterator not dereferencable". The gridMatrix is a std::vector<std::vector<std::vector<AtomsCell< Atom<T> * > * > * > * > I added the typename and also the typedef but I still have the error. I will move for this idea of vect of vect* of vect* to use boost::multi_array I think, but still I want to understand were this is wrong. /// @brief destructor ~AtomsGrid(void) { // free all the memory for all the pointers inside gridMatrix (all except the Atom<T>* ) //typedef typename ::value_type value_type; typedef std::vector<AtomsCell< Atom<T>* >*> std_vectorOfAtomsCell; typedef std::vector<std_vectorOfAtomsCell*> std_vectorOfVectorOfAtomsCell; std_vectorOfAtomsCell* vectorOfAtomsCell; std_vectorOfVectorOfAtomsCell* vectorOfVecOfAtomsCell; typename std_vectorOfVectorOfAtomsCell::iterator itSecond; typename std_vectorOfVectorOfAtomsCell::reverse_iterator reverseItSecond; typename std::vector<std_vectorOfVectorOfAtomsCell*>::iterator itFirst; //typename std::vector<AtomsCell< Atom<T>* >*>* vectorOfAtomsCell; //typename std::vector<std::vector<AtomsCell< Atom<T>* >*>*>* vectorOfVecOfAtomsCell; //typename std::vector<std::vector<AtomsCell< Atom<T>* >*>*>::iterator itSecond; //typename std::vector<std::vector<AtomsCell< Atom<T>* >*>*>::reverse_iterator reverseItSecond; //typename std::vector<std::vector<std::vector<AtomsCell< Atom<T>* >*>*>*>::iterator itFirst; for (itFirst = gridMatrix.begin(); itFirst != gridMatrix.end(); ++itFirst) { vectorOfVecOfAtomsCell = (*itFirst); while (!vectorOfVecOfAtomsCell->empty()) { reverseItSecond = vectorOfVecOfAtomsCell->rbegin(); itSecond = vectorOfVecOfAtomsCell->rbegin().base(); vectorOfAtomsCell = (*itSecond); // ERROR during run: "vector iterator not dereferencable" // I think the ERROR is because I need some typedef typename or template ???!!! // the error seems here event at itFirst //fr_Myit_Utils::vectorElementDeleter(*vectorOfAtomsCell); //vectorOfVecOfAtomsCell->pop_back(); } } fr_Myit_Utils::vectorElementDeleter(gridMatrix); } If someone want the full code that create the error I'm happy to give it but I do not think we can attach file in the forum. BUT still its is not very big so if you want it I can copy past it here. Thanks

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• Maps with a nested vector

  - by wawiti

  For some reason the compiler won't let me retrieve the vector of integers from the map that I've created, I want to be able to overwrite this vector with a new vector. The error the compiler gives me is ridiculous. Thanks for your help!! The compiler didn't like this part of my code: line_num = miss_words[word_1]; Error: [Wawiti@localhost Lab2]$ g++ -g -Wall *.cpp -o lab2 main.cpp: In function ‘int main(int, char**)’: main.cpp:156:49: error: no match for ‘operator=’ in ‘miss_words.std::map<_Key, _Tp, _Compare, _Alloc>::operator[]<std::basic_string<char>, std::vector<int>, std::less<std::basic_string<char> >, std::allocator<std::pair<const std::basic_string<char>, std::vector<int> > > >((*(const key_type*)(& word_1))) = line_num.std::vector<_Tp, _Alloc>::push_back<int, std::allocator<int> >((*(const value_type*)(& line)))’ main.cpp:156:49: note: candidate is: In file included from /usr/lib/gcc/x86_64-redhat->linux/4.7.2/../../../../include/c++/4.7.2vector:70:0, from header.h:19, from main.cpp:15: /usr/lib/gcc/x86_64-redhat-linux/4.7.2/../../../../include/c++/4.7.2/bits/vector.tcc:161:5: note: std::vector<_Tp, _Alloc>& std::vector<_Tp, _Alloc>::operator=(const std::vector<_Tp, _Alloc>&) [with _Tp = int; _Alloc = std::allocator<int>] /usr/lib/gcc/x86_64-redhat-linux/4.7.2/../../../../include/c++/4.7.2/bits/vector.tcc:161:5: note: no known conversion for argument 1 from ‘void’ to ‘const std::vector<int>&’ CODE: map<string, vector<int> > miss_words; // Creates a map for misspelled words string word_1; // String for word; string sentence; // To store each line; vector<int> line_num; // To store line numbers ifstream file; // Opens file to be spell checked file.open(argv[2]); int line = 1; while(getline(file, sentence)) // Reads in file sentence by sentence { sentence=remove_punct(sentence); // Removes punctuation from sentence stringstream pars_sentence; // Creates stringstream pars_sentence << sentence; // Places sentence in a stringstream while(pars_sentence >> word_1) // Picks apart sentence word by word { if(dictionary.find(word_1)==dictionary.end()) { line_num = miss_words[word_1]; //Compiler doesn't like this miss_words[word_1] = line_num.push_back(line); } } line++; // Increments line marker }

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• c++ template function compiles in header but not implementation

  - by flies

  I'm trying to learn templates and I've run into this confounding error. I'm declaring some functions in a header file and I want to make a separate implementation file where the functions will be defined. Here's the code that calls the header (dum.cpp): #include <iostream> #include <vector> #include <string> #include "dumper2.h" int main() { std::vector<int> v; for (int i=0; i<10; i++) { v.push_back(i); } test(); std::string s = ", "; dumpVector(v,s); } now, here's a working header file (dumper2.h): #include <iostream> #include <string> #include <vector> void test(); template <class T> void dumpVector( std::vector<T> v,std::string sep); template <class T> void dumpVector(std::vector<T> v, std::string sep) { typename std::vector<T>::iterator vi; vi = v.begin(); std::cout << *vi; vi++; for (;vi<v.end();vi++) { std::cout << sep << *vi ; } std::cout << "\n"; return; } with implentation (dumper2.cpp): #include <iostream> #include "dumper2.h" void test() { std::cout << "!olleh dlrow\n"; } the weird thing is that if I move the code that defines dumpVector from the .h to the .cpp file, I get the following error: g++ -c dumper2.cpp -Wall -Wno-deprecated g++ dum.cpp -o dum dumper2.o -Wall -Wno-deprecated /tmp/ccKD2e3G.o: In function `main': dum.cpp:(.text+0xce): undefined reference to `void dumpVector<int>(std::vector<int, std::allocator<int> >, std::basic_string<char, std::char_traits<char>, std::allocator<char> >)' collect2: ld returned 1 exit status make: *** [dum] Error 1 So why does it work one way and not the other? Clearly the compiler can find test(), so why can't it find dumpVector?

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• How can I copy one map into another using std::copy?

  - by Frank

  I would like to copy the content of one std::map into another. Can I use std::copy for that? Obviously, the following code won't work: int main() { typedef std::map<int,double> Map; Map m1; m1[3] = 0.3; m1[5] = 0.5; Map m2; m2[1] = 0.1; std::copy(m1.begin(), m1.end(), m2.begin()); return 0; } Is there any way to make it work with std::copy? Thanks!

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• Questions about game states

  - by MrPlow

  I'm trying to make a framework for a game I've wanted to do for quite a while. The first thing that I decided to implement was a state system for game states. When my "original" idea of having a doubly linked list of game states failed I found This blog and liked the idea of a stack based game state manager. However there were a few things I found weird: Instead of RAII two class methods are used to initialize and destroy the state Every game state class is a singleton(and singletons are bad aren't they?) Every GameState object is static So I took the idea and altered a few things and got this: GameState.h class GameState { private: bool m_paused; protected: StateManager& m_manager; public: GameState(StateManager& manager) : m_manager(manager), m_paused(false){} virtual ~GameState() {} virtual void update() = 0; virtual void draw() = 0; virtual void handleEvents() = 0; void pause() { m_paused = true; } void resume() { m_paused = false; } void changeState(std::unique_ptr<GameState> state) { m_manager.changeState(std::move(state)); } }; StateManager.h class GameState; class StateManager { private: std::vector< std::unique_ptr<GameState> > m_gameStates; public: StateManager(); void changeState(std::unique_ptr<GameState> state); void StateManager::pushState(std::unique_ptr<GameState> state); void popState(); void update(); void draw(); void handleEvents(); }; StateManager.cpp StateManager::StateManager() {} void StateManager::changeState( std::unique_ptr<GameState> state ) { if(!m_gameStates.empty()) { m_gameStates.pop_back(); } m_gameStates.push_back( std::move(state) ); } void StateManager::pushState(std::unique_ptr<GameState> state) { if(!m_gameStates.empty()) { m_gameStates.back()->pause(); } m_gameStates.push_back( std::move(state) ); } void StateManager::popState() { if(!m_gameStates.empty()) m_gameStates.pop_back(); } void StateManager::update() { if(!m_gameStates.empty()) m_gameStates.back()->update(); } void StateManager::draw() { if(!m_gameStates.empty()) m_gameStates.back()->draw(); } void StateManager::handleEvents() { if(!m_gameStates.empty()) m_gameStates.back()->handleEvents(); } And it's used like this: main.cpp StateManager states; states.changeState( std::unique_ptr<GameState>(new GameStateIntro(states)) ); while(gamewindow::gameWindow.isOpen()) { states.handleEvents(); states.update(); states.draw(); } Constructors/Destructors are used to create/destroy states instead of specialized class methods, state objects are no longer static but

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• boost.serialization and lazy initialization

  - by niXman

  i need to serialize directory tree. i have no trouble with this type: std::map< std::string, // string(path name) std::vector<std::string> // string array(file names in the path) > tree; but for the serialization the directory tree with the content i need other type: std::map< std::string, // string(path name) std::vector< // files array std::pair< std::string, // file name std::vector< // array of file pieces std::pair< // <<<<<<<<<<<<<<<<<<<<<< for this i need lazy initialization std::string, // piece buf boost::uint32_t // crc32 summ on piece > > > > > tree; how can i serialize the object of type "std::pair" in the moment of its serialization?

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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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• Why it's can be compiled in GNU/C++, can't compiled in VC++2010 RTM?

  - by volnet

  #include #include #include #include "copy_of_auto_ptr.h" #ifdef _MSC_VER #pragma message("#include ") #include // http://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas #endif /* case 1-4 is the requirement of the auto_ptr. which form http://ptgmedia.pearsoncmg.com/images/020163371X/autoptrupdate/auto_ptr_update.html */ /* case 1. (1) Direct-initialization, same type, e.g. */ std::auto_ptr source_int() { // return std::auto_ptr(new int(3)); std::auto_ptr tmp(new int(3)); return tmp; } /* case 2. (2) Copy-initialization, same type, e.g. */ void sink_int(std::auto_ptr p) { std::cout source_derived() { // return std::auto_ptr(new Derived()); std::auto_ptr tmp(new Derived()); return tmp; } /* case 4. (4) Copy-initialization, base-from-derived, e.g. */ void sink_base( std::auto_ptr p) { p-go(); } int main(void) { /* // auto_ptr */ // case 1. // auto_ptr std::auto_ptr p_int(source_int()); std::cout p_derived(source_derived()); p_derived-go(); // case 4. // auto_ptr sink_base(source_derived()); return 0; } In Eclipse(GNU C++.exe -v gcc version 3.4.5 (mingw-vista special r3)) it's two compile error: Description Resource Path Location Type initializing argument 1 of void sink_base(std::auto_ptr<Base>)' from result ofstd::auto_ptr<_Tp::operator std::auto_ptr<_Tp1() [with _Tp1 = Base, _Tp = Derived]' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem Description Resource Path Location Type no matching function for call to `std::auto_ptr::auto_ptr(std::auto_ptr)' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem But it's right in VS2010 RTM. Questions: Which compiler stand for the ISO C++ standard? The content of case 4 is the problem "auto_ptr & auto_ptr_ref want to resolve?"

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• How to use boost::transform_iterator to iterate over modifed std::map values?

  - by Frank

  I have an std::map, and I would like to define an iterator that returns modified values. Typically, a std::map<int,double>::iterator iterates over std::pair<int,double>, and I would like the same behavior, just the double value is multiplied by a constant. I tried it with boost::transform_iterator, but it doesn't compile: #include <map> #include <boost/iterator/transform_iterator.hpp> #include <boost/functional.hpp> typedef std::map<int,double> Map; Map m; m[100] = 2.24; typedef boost::binder2nd< std::multiplies<double> > Function; typedef boost::transform_iterator<Function, Map::value_type*> MultiplyIter; MultiplyIter begin = boost::make_transform_iterator(m.begin(), Function(std::multiplies<double>(), 4)); // now want to similarly create an end iterator // and then iterate over the modified map The error is: error: conversion from 'boost ::transform_iterator< boost::binder2nd<multiplies<double> >, gen_map<int, double>::iterator , boost::use_default, boost::use_default >' to non-scalar type 'boost::transform_iterator< boost::binder2nd<multiplies<double> >, pair<const int, double> * , boost::use_default, boost::use_default >' requested What is gen_map and do I really need it? I adapted the transform_iterator tutorial code from here to write this code ...

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• Getting value of LSB from Hex (C code)

  - by Rjff

  Hi - first post here :) I've got a code like this in C: unsigned char const data[ ] = {0x0a, 0x1d, 0xf0, 0x07}; I need to extract it such that the final value is: 0xa1df7 I have only been able to extract and get it working if the hex values that have at least 1 zero: unsigned char const data[ ] = {0x0a, 0xd0, 0xf0, 0x07}; using the code below: for(int i = 0; i < SIZE; ++i) { tmp = data[i]; if ( (data[i] <= 0x0F) && (((data[i] & 0x0F) == 0) || (data[i] & 0xF0) == 0)) // one of the hex is zero { tmp = ((tmp << 4) >> 4) << N[i]; std::cout << "foo: " << std::hex << tmp << ":" << std::endl; } else if ((data[i] >= 0x0F) && (((data[i] & 0x0F) == 0) || (data[i] & 0xF0) == 0) ) { tmp = (tmp >> 4) << N[i]; std::cout << "bar: " << std::hex << tmp << ":" << std::endl; } else { std::cout << "result: " << std::hex << result << ":" << std::endl; std::cout << "tmp << 8: " << std::hex << (tmp << 8)<< ":" << std::endl; result = result | (tmp << 8); std::cout << "result |= (tmp << 8): " << std::hex << result << ":" << std::endl; } result |= tmp; std::cout << "boo: " << std::hex << result << ":" << std::endl; } It seems the last else {...} block is troublesome for me. Any ideas? Thanks!

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• DirectX11 CreateWICTextureFromMemory Using PNG

  - by seethru

  I've currently got textures loading using CreateWICTextureFromFile however I'd like a little more control over it, and I'd like to store images in their byte form in a resource loader. Below is just two sets of test code that return two separate results and I'm looking for any insight into a possible solution. ID3D11ShaderResourceView* srv; std::basic_ifstream<unsigned char> file("image.png", std::ios::binary); file.seekg(0,std::ios::end); int length = file.tellg(); file.seekg(0,std::ios::beg); unsigned char* buffer = new unsigned char[length]; file.read(&buffer[0],length); file.close(); HRESULT hr; hr = DirectX::CreateWICTextureFromMemory(_D3D->GetDevice(), _D3D->GetDeviceContext(), &buffer[0], sizeof(buffer), nullptr, &srv, NULL); As a return for the above code I get Component not found. std::ifstream file; ID3D11ShaderResourceView* srv; file.open("../Assets/Textures/osg.png", std::ios::binary); file.seekg(0,std::ios::end); int length = file.tellg(); file.seekg(0,std::ios::beg); std::vector<char> buffer(length); file.read(&buffer[0],length); file.close(); HRESULT hr; hr = DirectX::CreateWICTextureFromMemory(_D3D->GetDevice(), _D3D->GetDeviceContext(), (const uint8_t*)&buffer[0], sizeof(buffer), nullptr, &srv, NULL); The above code returns that the image format is unknown. I'm clearly doing something wrong here, any help is greatly appreciated. Tried finding anything even similar on stackoverflow, and google to no avail.

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• C++0x Overload on reference, versus sole pass-by-value + std::move?

  - by dean

  It seems the main advice concerning C++0x's rvalues is to add move constructors and move operators to your classes, until compilers default-implement them. But waiting is a losing strategy if you use VC10, because automatic generation probably won't be here until VC10 SP1, or in worst case, VC11. Likely, the wait for this will be measured in years. Here lies my problem. Writing all this duplicate code is not fun. And it's unpleasant to look at. But this is a burden well received, for those classes deemed slow. Not so for the hundreds, if not thousands, of smaller classes. ::sighs:: C++0x was supposed to let me write less code, not more! And then I had a thought. Shared by many, I would guess. Why not just pass everything by value? Won't std::move + copy elision make this nearly optimal? Example 1 - Typical Pre-0x constructor OurClass::OurClass(const SomeClass& obj) : obj(obj) {} SomeClass o; OurClass(o); // single copy OurClass(std::move(o)); // single copy OurClass(SomeClass()); // single copy Cons: A wasted copy for rvalues. Example 2 - Recommended C++0x? OurClass::OurClass(const SomeClass& obj) : obj(obj) {} OurClass::OurClass(SomeClass&& obj) : obj(std::move(obj)) {} SomeClass o; OurClass(o); // single copy OurClass(std::move(o)); // zero copies, one move OurClass(SomeClass()); // zero copies, one move Pros: Presumably the fastest. Cons: Lots of code! Example 3 - Pass-by-value + std::move OurClass::OurClass(SomeClass obj) : obj(std::move(obj)) {} SomeClass o; OurClass(o); // single copy, one move OurClass(std::move(o)); // zero copies, two moves OurClass(SomeClass()); // zero copies, one move Pros: No additional code. Cons: A wasted move in cases 1 & 2. Performance will suffer greatly if SomeClass has no move constructor. What do you think? Is this correct? Is the incurred move a generally acceptable loss when compared to the benefit of code reduction?

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• Troubleshoot Perl module installation on Mac OS X

  - by Daniel Standage

  I'm trying to install the Perl module Set::IntervalTree on Mac OS X. I recently installed it today on an Ubuntu box with no problem. I simply started cpan, entered install Set:IntervalTree, and it all worked out. However, the installation failed on Mac OS X--it spits out a huge list of compiler errors (below). How would I troubleshoot this. I don't even know where to begin. cpan[1]> install Set::IntervalTree CPAN: Storable loaded ok (v2.18) Going to read /Users/standage/.cpan/Metadata Database was generated on Fri, 14 Jan 2011 02:58:42 GMT CPAN: YAML loaded ok (v0.72) Going to read /Users/standage/.cpan/build/ ............................................................................DONE Found 1 old build, restored the state of 1 Running install for module 'Set::IntervalTree' Running make for B/BE/BENBOOTH/Set-IntervalTree-0.01.tar.gz CPAN: Digest::SHA loaded ok (v5.45) CPAN: Compress::Zlib loaded ok (v2.008) Checksum for /Users/standage/.cpan/sources/authors/id/B/BE/BENBOOTH/Set-IntervalTree-0.01.tar.gz ok Scanning cache /Users/standage/.cpan/build for sizes ............................................................................DONE x Set-IntervalTree-0.01/ x Set-IntervalTree-0.01/src/ x Set-IntervalTree-0.01/src/Makefile x Set-IntervalTree-0.01/src/interval_tree.h x Set-IntervalTree-0.01/src/test_main.cc x Set-IntervalTree-0.01/lib/ x Set-IntervalTree-0.01/lib/Set/ x Set-IntervalTree-0.01/lib/Set/IntervalTree.pm x Set-IntervalTree-0.01/Changes x Set-IntervalTree-0.01/MANIFEST x Set-IntervalTree-0.01/t/ x Set-IntervalTree-0.01/t/Set-IntervalTree.t x Set-IntervalTree-0.01/typemap x Set-IntervalTree-0.01/perlobject.map x Set-IntervalTree-0.01/IntervalTree.xs x Set-IntervalTree-0.01/Makefile.PL x Set-IntervalTree-0.01/README x Set-IntervalTree-0.01/META.yml CPAN: File::Temp loaded ok (v0.18) CPAN.pm: Going to build B/BE/BENBOOTH/Set-IntervalTree-0.01.tar.gz Checking if your kit is complete... Looks good Writing Makefile for Set::IntervalTree cp lib/Set/IntervalTree.pm blib/lib/Set/IntervalTree.pm AutoSplitting blib/lib/Set/IntervalTree.pm (blib/lib/auto/Set/IntervalTree) /usr/bin/perl /System/Library/Perl/5.10.0/ExtUtils/xsubpp -C++ -typemap /System/Library/Perl/5.10.0/ExtUtils/typemap -typemap perlobject.map -typemap typemap IntervalTree.xs > IntervalTree.xsc && mv IntervalTree.xsc IntervalTree.c g++ -c -Isrc -arch x86_64 -arch i386 -arch ppc -g -pipe -fno-common -DPERL_DARWIN -fno-strict-aliasing -I/usr/local/include -g -O0 -DVERSION=\"0.01\" -DXS_VERSION=\"0.01\" "-I/System/Library/Perl/5.10.0/darwin-thread-multi-2level/CORE" -Isrc IntervalTree.c In file included from /usr/include/c++/4.2.1/bits/basic_ios.h:44, from /usr/include/c++/4.2.1/ios:50, from /usr/include/c++/4.2.1/ostream:45, from /usr/include/c++/4.2.1/iostream:45, from IntervalTree.xs:16: /usr/include/c++/4.2.1/bits/locale_facets.h:4420:40: error: macro "do_open" requires 7 arguments, but only 2 given /usr/include/c++/4.2.1/bits/locale_facets.h:4467:34: error: macro "do_close" requires 2 arguments, but only 1 given /usr/include/c++/4.2.1/bits/locale_facets.h:4486:55: error: macro "do_open" requires 7 arguments, but only 2 given /usr/include/c++/4.2.1/bits/locale_facets.h:4513:23: error: macro "do_close" requires 2 arguments, but only 1 given In file included from /usr/include/c++/4.2.1/bits/locale_facets.h:4599, from /usr/include/c++/4.2.1/bits/basic_ios.h:44, from /usr/include/c++/4.2.1/ios:50, from /usr/include/c++/4.2.1/ostream:45, from /usr/include/c++/4.2.1/iostream:45, from IntervalTree.xs:16: /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:58:38: error: macro "do_open" requires 7 arguments, but only 2 given /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:67:71: error: macro "do_open" requires 7 arguments, but only 2 given /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:78:39: error: macro "do_close" requires 2 arguments, but only 1 given In file included from /usr/include/c++/4.2.1/bits/basic_ios.h:44, from /usr/include/c++/4.2.1/ios:50, from /usr/include/c++/4.2.1/ostream:45, from /usr/include/c++/4.2.1/iostream:45, from IntervalTree.xs:16: /usr/include/c++/4.2.1/bits/locale_facets.h:4486: error: ‘do_open’ declared as a ‘virtual’ field /usr/include/c++/4.2.1/bits/locale_facets.h:4486: error: expected ‘;’ before ‘const’ /usr/include/c++/4.2.1/bits/locale_facets.h:4513: error: variable or field ‘do_close’ declared void /usr/include/c++/4.2.1/bits/locale_facets.h:4513: error: expected ‘;’ before ‘const’ In file included from /usr/include/c++/4.2.1/bits/locale_facets.h:4599, from /usr/include/c++/4.2.1/bits/basic_ios.h:44, from /usr/include/c++/4.2.1/ios:50, from /usr/include/c++/4.2.1/ostream:45, from /usr/include/c++/4.2.1/iostream:45, from IntervalTree.xs:16: /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:67: error: expected initializer before ‘const’ /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64/bits/messages_members.h:78: error: expected initializer before ‘const’ In file included from IntervalTree.xs:19: src/interval_tree.h:95: error: type/value mismatch at argument 1 in template parameter list for ‘template<class _Tp, class _Alloc> class std::vector’ src/interval_tree.h:95: error: expected a type, got ‘IntervalTree<T,N>::it_recursion_node’ src/interval_tree.h:95: error: template argument 2 is invalid src/interval_tree.h: In constructor ‘IntervalTree<T, N>::IntervalTree()’: src/interval_tree.h:130: error: expected type-specifier src/interval_tree.h:130: error: expected `;' src/interval_tree.h:135: error: expected type-specifier src/interval_tree.h:135: error: expected `;' src/interval_tree.h:141: error: request for member ‘push_back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h: In member function ‘void IntervalTree<T, N>::LeftRotate(IntervalTree<T, N>::Node*)’: src/interval_tree.h:178: error: ‘y’ was not declared in this scope src/interval_tree.h: In member function ‘void IntervalTree<T, N>::RightRotate(IntervalTree<T, N>::Node*)’: src/interval_tree.h:240: error: ‘x’ was not declared in this scope src/interval_tree.h: In member function ‘void IntervalTree<T, N>::TreeInsertHelp(IntervalTree<T, N>::Node*)’: src/interval_tree.h:298: error: ‘x’ was not declared in this scope src/interval_tree.h:299: error: ‘y’ was not declared in this scope src/interval_tree.h: In member function ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N)’: src/interval_tree.h:375: error: ‘y’ was not declared in this scope src/interval_tree.h:376: error: ‘x’ was not declared in this scope src/interval_tree.h:377: error: ‘newNode’ was not declared in this scope src/interval_tree.h:379: error: expected type-specifier src/interval_tree.h:379: error: expected `;' src/interval_tree.h: In member function ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::GetSuccessorOf(IntervalTree<T, N>::Node*) const’: src/interval_tree.h:450: error: ‘y’ was not declared in this scope src/interval_tree.h: In member function ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::GetPredecessorOf(IntervalTree<T, N>::Node*) const’: src/interval_tree.h:483: error: ‘y’ was not declared in this scope src/interval_tree.h: In destructor ‘IntervalTree<T, N>::~IntervalTree()’: src/interval_tree.h:546: error: ‘x’ was not declared in this scope src/interval_tree.h:547: error: type/value mismatch at argument 1 in template parameter list for ‘template<class _Tp, class _Alloc> class std::vector’ src/interval_tree.h:547: error: expected a type, got ‘(IntervalTree<T,N>::Node * <expression error>)’ src/interval_tree.h:547: error: template argument 2 is invalid src/interval_tree.h:547: error: invalid type in declaration before ‘;’ token src/interval_tree.h:551: error: request for member ‘push_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:554: error: request for member ‘push_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:557: error: request for member ‘empty’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:558: error: request for member ‘back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:559: error: request for member ‘pop_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:561: error: request for member ‘push_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h:564: error: request for member ‘push_back’ in ‘stuffToFree’, which is of non-class type ‘int’ src/interval_tree.h: In member function ‘void IntervalTree<T, N>::DeleteFixUp(IntervalTree<T, N>::Node*)’: src/interval_tree.h:613: error: ‘w’ was not declared in this scope src/interval_tree.h:614: error: ‘rootLeft’ was not declared in this scope src/interval_tree.h: In member function ‘T IntervalTree<T, N>::remove(IntervalTree<T, N>::Node*)’: src/interval_tree.h:697: error: ‘y’ was not declared in this scope src/interval_tree.h:698: error: ‘x’ was not declared in this scope src/interval_tree.h: In member function ‘std::vector<T, std::allocator<_CharT> > IntervalTree<T, N>::fetch(N, N)’: src/interval_tree.h:819: error: ‘x’ was not declared in this scope src/interval_tree.h:833: error: invalid types ‘int[size_t]’ for array subscript src/interval_tree.h:836: error: request for member ‘push_back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:837: error: request for member ‘back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:838: error: request for member ‘back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:839: error: request for member ‘back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:840: error: request for member ‘size’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:846: error: request for member ‘size’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:847: error: expected `;' before ‘back’ src/interval_tree.h:848: error: request for member ‘pop_back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:850: error: ‘back’ was not declared in this scope src/interval_tree.h:853: error: invalid types ‘int[size_t]’ for array subscript IntervalTree.c: In function ‘void boot_Set__IntervalTree(PerlInterpreter*, CV*)’: IntervalTree.c:365: warning: deprecated conversion from string constant to ‘char*’ src/interval_tree.h: In constructor ‘IntervalTree<T, N>::IntervalTree() [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.c:67: instantiated from here src/interval_tree.h:130: error: cannot convert ‘int*’ to ‘IntervalTree<std::tr1::shared_ptr<sv>, long int>::Node*’ in assignment src/interval_tree.h:135: error: cannot convert ‘int*’ to ‘IntervalTree<std::tr1::shared_ptr<sv>, long int>::Node*’ in assignment ...blah blah blah... ...blah blah blah... ...blah blah blah... ...blah blah blah... ...blah blah blah... ...blah blah blah... src/interval_tree.h:848: error: request for member ‘pop_back’ in ‘((IntervalTree<T, N>*)this)->IntervalTree<T, N>::recursionNodeStack’, which is of non-class type ‘int’ src/interval_tree.h:850: error: ‘back’ was not declared in this scope src/interval_tree.h:853: error: invalid types ‘int[size_t]’ for array subscript IntervalTree.c: In function ‘void boot_Set__IntervalTree(PerlInterpreter*, CV*)’: IntervalTree.c:365: warning: deprecated conversion from string constant to ‘char*’ src/interval_tree.h: In constructor ‘IntervalTree<T, N>::IntervalTree() [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.c:67: instantiated from here src/interval_tree.h:130: error: cannot convert ‘int*’ to ‘IntervalTree<std::tr1::shared_ptr<sv>, long int>::Node*’ in assignment src/interval_tree.h:135: error: cannot convert ‘int*’ to ‘IntervalTree<std::tr1::shared_ptr<sv>, long int>::Node*’ in assignment src/interval_tree.h: In member function ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.xs:57: instantiated from here src/interval_tree.h:375: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:375: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h:376: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:376: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h:377: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:377: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h: In member function ‘std::vector<T, std::allocator<_CharT> > IntervalTree<T, N>::fetch(N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.xs:65: instantiated from here src/interval_tree.h:819: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:819: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant IntervalTree.xs:65: instantiated from here src/interval_tree.h:847: error: dependent-name ‘IntervalTree<T,N>::it_recursion_node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:847: note: say ‘typename IntervalTree<T,N>::it_recursion_node’ if a type is meant src/interval_tree.h: In destructor ‘IntervalTree<T, N>::~IntervalTree() [with T = std::tr1::shared_ptr<sv>, N = long int]’: IntervalTree.c:205: instantiated from here src/interval_tree.h:546: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:546: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h: In member function ‘void IntervalTree<T, N>::TreeInsertHelp(IntervalTree<T, N>::Node*) [with T = std::tr1::shared_ptr<sv>, N = long int]’: src/interval_tree.h:380: instantiated from ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’ IntervalTree.xs:57: instantiated from here src/interval_tree.h:298: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:298: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h:299: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:299: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h: In member function ‘void IntervalTree<T, N>::LeftRotate(IntervalTree<T, N>::Node*) [with T = std::tr1::shared_ptr<sv>, N = long int]’: src/interval_tree.h:395: instantiated from ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’ IntervalTree.xs:57: instantiated from here src/interval_tree.h:178: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:178: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant src/interval_tree.h: In member function ‘void IntervalTree<T, N>::RightRotate(IntervalTree<T, N>::Node*) [with T = std::tr1::shared_ptr<sv>, N = long int]’: src/interval_tree.h:399: instantiated from ‘typename IntervalTree<T, N>::Node* IntervalTree<T, N>::insert(const T&, N, N) [with T = std::tr1::shared_ptr<sv>, N = long int]’ IntervalTree.xs:57: instantiated from here src/interval_tree.h:240: error: dependent-name ‘IntervalTree<T,N>::Node’ is parsed as a non-type, but instantiation yields a type src/interval_tree.h:240: note: say ‘typename IntervalTree<T,N>::Node’ if a type is meant lipo: can't open input file: /var/tmp//ccLthuaw.out (No such file or directory) make: *** [IntervalTree.o] Error 1 BENBOOTH/Set-IntervalTree-0.01.tar.gz make -- NOT OK Running make test Can't test without successful make Running make install Make had returned bad status, install seems impossible Failed during this command: BENBOOTH/Set-IntervalTree-0.01.tar.gz : make NO

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• What container type provides better (average) performance than std::map?

  - by Truncheon

  In the following example a std::map structure is filled with 26 values from A - Z (for key) and 0 - 26 for value. The time taken (on my system) to lookup the last entry (10000000 times) is roughly 250 ms for the vector, and 125 ms for the map. (I compiled using release mode, with O3 option turned on for g++ 4.4) But if for some odd reason I wanted better performance than the std::map, what data structures and functions would I need to consider using? I apologize if the answer seems obvious to you, but I haven't had much experience in the performance critical aspects of C++ programming. UPDATE: This example is rather trivial and hides the true complexity of what I'm trying to achieve. My real world project is a simple scripting language that uses a parser, data tree, and interpreter (instead of a VM stack system). I need to use some kind of data structure (perhaps map) to store the variables names created by script programmers. These are likely to be pretty randomly named, so I need a lookup method that can quickly find a particular key within a (probably) fairly large list of names. #include <ctime> #include <map> #include <vector> #include <iostream> struct mystruct { char key; int value; mystruct(char k = 0, int v = 0) : key(k), value(v) { } }; int find(const std::vector<mystruct>& ref, char key) { for (std::vector<mystruct>::const_iterator i = ref.begin(); i != ref.end(); ++i) if (i->key == key) return i->value; return -1; } int main() { std::map<char, int> mymap; std::vector<mystruct> myvec; for (int i = 'a'; i < 'a' + 26; ++i) { mymap[i] = i - 'a'; myvec.push_back(mystruct(i, i - 'a')); } int pre = clock(); for (int i = 0; i < 10000000; ++i) { find(myvec, 'z'); } std::cout << "linear scan: milli " << clock() - pre << "\n"; pre = clock(); for (int i = 0; i < 10000000; ++i) { mymap['z']; } std::cout << "map scan: milli " << clock() - pre << "\n"; return 0; }

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• Boost Spirit and Lex parser problem

  - by bpw1621

  I've been struggling to try and (incrementally) modify example code from the documentation but with not much different I am not getting the behavior I expect. Specifically, the "if" statement fails when (my intent is that) it should be passing (there was an "else" but that part of the parser was removed during debugging). The assignment statement works fine. I had a "while" statement as well which had the same problem as the "if" statement so I am sure if I can get help to figure out why one is not working it should be easy to get the other going. It must be kind of subtle because this is almost verbatim what is in one of the examples. #include <iostream> #include <fstream> #include <string> #define BOOST_SPIRIT_DEBUG #include <boost/config/warning_disable.hpp> #include <boost/spirit/include/qi.hpp> #include <boost/spirit/include/lex_lexertl.hpp> #include <boost/spirit/include/phoenix_operator.hpp> #include <boost/spirit/include/phoenix_statement.hpp> #include <boost/spirit/include/phoenix_container.hpp> namespace qi = boost::spirit::qi; namespace lex = boost::spirit::lex; inline std::string read_from_file( const char* infile ) { std::ifstream instream( infile ); if( !instream.is_open() ) { std::cerr << "Could not open file: \"" << infile << "\"" << std::endl; exit( -1 ); } instream.unsetf( std::ios::skipws ); return( std::string( std::istreambuf_iterator< char >( instream.rdbuf() ), std::istreambuf_iterator< char >() ) ); } template< typename Lexer > struct LangLexer : lex::lexer< Lexer > { LangLexer() { identifier = "[a-zA-Z][a-zA-Z0-9_]*"; number = "[-+]?(\\d*\\.)?\\d+([eE][-+]?\\d+)?"; if_ = "if"; else_ = "else"; this->self = lex::token_def<> ( '(' ) | ')' | '{' | '}' | '=' | ';'; this->self += identifier | number | if_ | else_; this->self( "WS" ) = lex::token_def<>( "[ \\t\\n]+" ); } lex::token_def<> if_, else_; lex::token_def< std::string > identifier; lex::token_def< double > number; }; template< typename Iterator, typename Lexer > struct LangGrammar : qi::grammar< Iterator, qi::in_state_skipper< Lexer > > { template< typename TokenDef > LangGrammar( const TokenDef& tok ) : LangGrammar::base_type( program ) { using boost::phoenix::val; using boost::phoenix::ref; using boost::phoenix::size; program = +block; block = '{' >> *statement >> '}'; statement = assignment | if_stmt; assignment = ( tok.identifier >> '=' >> expression >> ';' ); if_stmt = ( tok.if_ >> '(' >> expression >> ')' >> block ); expression = ( tok.identifier[ qi::_val = qi::_1 ] | tok.number[ qi::_val = qi::_1 ] ); BOOST_SPIRIT_DEBUG_NODE( program ); BOOST_SPIRIT_DEBUG_NODE( block ); BOOST_SPIRIT_DEBUG_NODE( statement ); BOOST_SPIRIT_DEBUG_NODE( assignment ); BOOST_SPIRIT_DEBUG_NODE( if_stmt ); BOOST_SPIRIT_DEBUG_NODE( expression ); } qi::rule< Iterator, qi::in_state_skipper< Lexer > > program, block, statement; qi::rule< Iterator, qi::in_state_skipper< Lexer > > assignment, if_stmt; typedef boost::variant< double, std::string > expression_type; qi::rule< Iterator, expression_type(), qi::in_state_skipper< Lexer > > expression; }; int main( int argc, char** argv ) { typedef std::string::iterator base_iterator_type; typedef lex::lexertl::token< base_iterator_type, boost::mpl::vector< double, std::string > > token_type; typedef lex::lexertl::lexer< token_type > lexer_type; typedef LangLexer< lexer_type > LangLexer; typedef LangLexer::iterator_type iterator_type; typedef LangGrammar< iterator_type, LangLexer::lexer_def > LangGrammar; LangLexer lexer; LangGrammar grammar( lexer ); std::string str( read_from_file( 1 == argc ? "boostLexTest.dat" : argv[1] ) ); base_iterator_type strBegin = str.begin(); iterator_type tokenItor = lexer.begin( strBegin, str.end() ); iterator_type tokenItorEnd = lexer.end(); std::cout << std::setfill( '*' ) << std::setw(20) << '*' << std::endl << str << std::endl << std::setfill( '*' ) << std::setw(20) << '*' << std::endl; bool result = qi::phrase_parse( tokenItor, tokenItorEnd, grammar, qi::in_state( "WS" )[ lexer.self ] ); if( result ) { std::cout << "Parsing successful" << std::endl; } else { std::cout << "Parsing error" << std::endl; } return( 0 ); } Here is the output of running this (the file read into the string is dumped out first in main) ******************** { a = 5; if( a ){ b = 2; } } ******************** <program> <try>{</try> <block> <try>{</try> <statement> <try></try> <assignment> <try></try> <expression> <try></try> <success>;</success> <attributes>(5)</attributes> </expression> <success></success> <attributes>()</attributes> </assignment> <success></success> <attributes>()</attributes> </statement> <statement> <try></try> <assignment> <try></try> <fail/> </assignment> <if_stmt> <try> if(</try> <fail/> </if_stmt> <fail/> </statement> <fail/> </block> <fail/> </program> Parsing error

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• How can I have multiple layers in my map array?

  - by Manl400

  How do I load Levels in my game, as in Layer 1 would be Objects, Layer 2 would be Characters and so on. I only need 3 layers, and they will all be put on top of each other. i.e having a flower with a transparent background to be put on grass or dirt on the layer below.I would like to Read From the same file too. How would i go about doing this? Any help would be appreciated. I load the map from a level file which are just numbers corresponding to a tile in the tilesheet. Here is the level file [Layer1] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 [Layer2] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 [Layer3] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 And here is the code that interprets it void LoadMap(const char *filename, std::vector< std::vector <int> > &map) { std::ifstream openfile(filename); if(openfile.is_open()) { std::string line, value; int space; while(!openfile.eof()) { std::getline(openfile, line); if(line.find("[TileSet]") != std::string::npos) { state = TileSet; continue; } else if (line.find("[Layer1]") != std::string::npos) { state = Map; continue; } switch(state) { case TileSet: if(line.length() > 0) tileSet = al_load_bitmap(line.c_str()); break; case Map: std::stringstream str(line); std::vector<int> tempVector; while(!str.eof()) { std::getline(str, value, ' '); if(value.length() > 0) tempVector.push_back(atoi(value.c_str())); } map.push_back(tempVector); break; } } } else { } } and this is how it draws the map. Also the tile sheet is 1280 by 1280 and the tilesizeX and tilesizeY is 64 void DrawMap(std::vector <std::vector <int> > map) { int mapRowCount = map.size(); for(int i, j = 0; i < mapRowCount; i ++) { int mapColCount = map[i].size(); for (int j = 0; j < mapColCount; ++j) { int tilesetIndex = map[i][j]; int tilesetRow = floor(tilesetIndex / TILESET_COLCOUNT); int tilesetCol = tilesetIndex % TILESET_COLCOUNT; al_draw_bitmap_region(tileSet, tilesetCol * TileSizeX, tilesetRow * TileSizeY, TileSizeX, TileSizeY, j * TileSizeX, i * TileSizeX, NULL); } } } EDIT: http://i.imgur.com/Ygu0zRE.jpg

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