stl

问题 I have a vague memory of the STL having trouble with aligned structs (e.g. SIMD vectors placed in a std::vector), unless you specify a custom allocator. According to this document VS 2012/VC11 has partial support for c++ alignment. Does this mean that the VS STL implementation can handle aligned structs now, without providing a custom allocator? 回答1: No. It means that the VC++ compiler supports a method for specifying the required alignment for a type (the __declspec(align(N)) syntax). VC++

问题 I've got a class declared like this: class Level { private: std::vector<mapObject::MapObject> features; (...) }; and in one of its member functions I try to iterate through that vector like this: vector<mapObject::MapObject::iterator it; for(it=features.begin(); it<features.end(); it++) { /* loop code */ } This seems straightforward to me, but g++ gives me this error: src/Level.cpp:402: error: no match for ‘operator=’ in ‘it = ((const yarl::level::Level*)this)->yarl::level::Level::features

问题 I am very new to C++ and I am trying to implement a TriangleDynamic object that can recursively split itself using a function called splitTriangleProject. It splits itself into four smaller TriangleDynamic objects (and projects the vertices of the new triangles onto a sphere with a given radius and origin, but I believe this is beside the point), pushes the newly created triangles into a vector that is part of the member data of the original object. The vector member data is called

问题 As the title says multiset inserts a value at the end of the range of all the same values. (Ex: Inserting 2 in a multiset 1,2,2,3 makes it 1,2,2,/*new*/ 2,3 ). How do I get the new value inserted at the start of the range of all the same values? (Ex: Inserting 2 in multiset 1,2,2,3 should make 1,/*new*/ 2,2,2,3 ) 回答1: Try this std::multiset<int> mset { 2,4,5,5,6,6 }; int val = 5; auto it = mset.equal_range ( val ).first; //Find the first occurrence of your target value. Function will return

问题 While reading "c++ gui programming eith Qt 4 , second edition " I came across this topic : "The STL header provides a more complete set of generic algorithms. these algorithms can be used on Qt containers as well as STL containers. If STL implementations are available on all your platforms, there is probably no reason to avoid using the STL algorithms when Qt lacks an equivalent algorithm ." It states that the generic algorithms of STL(which is defined in "algorithm" header) can be used with

问题 I am trying to refactor some code that doesn't use the STL to use the generic algorithms it provide. I have a struct like this : struct A { int i; //other stuff... }; // ... A* array; // array of A objects, sorted by A::i member int n = ...; // array size there is then a function that was coded that takes A , n and an integer k , whose purpose is to give me pointers to to the first and the last element of the array that have their i member equal to k . This is implemented by hand in terms of

问题 What is the proper way to enable my swap in STL algorithms? 1) Member swap . Does std::swap use SFINAE trick to use the member swap . 2) Free standing swap in the same namespace. 3) Partial specialization of std::swap . 4) All of the above. Thank you. EDIT: Looks like I didn't word my question clearly. Basically, I have a template class and I need STL algos to use the (efficient) swap method I wrote for that class. 回答1: 1) is the proper use of swap . Write it this way when you write "library"

问题 In the STL implementation of VS10 there is the following code for a variant of std::swap(): // TEMPLATE FUNCTION _Move template<class _Ty> inline typename tr1::_Remove_reference<_Ty>::_Type&& _Move(_Ty&& _Arg) { // forward _Arg as movable return ((typename tr1::_Remove_reference<_Ty>::_Type&&)_Arg); } // TEMPLATE FUNCTION swap (from <algorithm>) template<class _Ty> inline void swap(_Ty& _Left, _Ty& _Right) { // exchange values stored at _Left and _Right _Ty _Tmp = _Move(_Left); _Left = _Move(

问题 Does any library has a Circular buffer class that can be used with pre-allocated buffer? I looked at Boost::circular_buffer, but it seems all of its constructors require an allocator. I don't want to reinvent circular buffer class, but have to use pre-allocated buffer. I want something like: char buffer[1000]; // pre-allocated buffer. circular_buffer_class cb; // a class that provides the interface as a circular buffer. cb.attach(buffer, 1000); // attaching the preallocated buffer to the

问题 I have this code: set<int>::iterator new_end = set_difference(set1.begin(), set1.end(), set2.begin(), set2.end(), set1.begin()); set1.erase(new_end, set1.end); It compiles and runs fine in visual studio. However, in a previous question, people stated that a set 's iterators are supposed to be const . I don't see anything like that in the standard. Can someone tell me where it says that, or if this is well-defined behavior? If it's not, please provide code that does what I need. Is there a way