template-meta-programming

问题 So, what I want is to create multidimensional vector of given type where the first dimension will have size of the first argument of a function call, etc, for example if I do std::size_t n = 5; auto x = make_vector<int>(n + 1, n * 2, n * 3); x should be 6x10x15 3d array (consisting of zeroes, because I want to default construct right now) I have tried this: template <typename T> std::vector<T> make_vector(std::size_t size) { return std::vector<T>(size); } template <typename T, typename...

问题 So, what I want is to create multidimensional vector of given type where the first dimension will have size of the first argument of a function call, etc, for example if I do std::size_t n = 5; auto x = make_vector<int>(n + 1, n * 2, n * 3); x should be 6x10x15 3d array (consisting of zeroes, because I want to default construct right now) I have tried this: template <typename T> std::vector<T> make_vector(std::size_t size) { return std::vector<T>(size); } template <typename T, typename...

问题 I have seen this question which allows one to check for the existence of a member function , but I'm trying to find out whether a class has a member type . In the example below, both evaluate to "false", but I would like to find a way so that has_bar<foo1>::value evaluates to false, and has_bar<foo2>::value evaluates to true . Is this possible? #include <iostream> struct foo1; struct foo2 { typedef int bar; }; template <typename T> class has_bar { typedef char yes; typedef long no; template

问题 I am currently doing some template metaprogramming. In my case I can handle any "iteratable" type, i.e. any type for which a typedef foo const_iterator exists in the same manner. I was trying to use the new C++11 template metaprogramming for this, however I could not find a method to detect if a certain type is missing. Because I also need to turn on/off other template specializations based on other characteristics, I am currently using a template with two parameters, and the second one gets

问题 I want to make a function which returns a power of integer. Please read the fmuecke's solution in power of an integer in c++ . However, I want to generalize his solution to the arbitrary type T. Since c++11 has constexpr, I guess this is possible. Naively, I tried something like, template<class T, int N> inline constexpr T pow(const T x){ return pow<N-1>(x) * x; } template<class T> inline constexpr T pow<T, 1>(const T x){ return x; } template<class T> inline constexpr T pow<T, 0>(const T x){

问题 I'm enjoying ramping up on variadic templates and have started fiddling about with this new feature. I'm trying to get my head around the implementation details of std::index_sequence 's (used for tuple implementation). I see sample code around there, but I really want a dumbed down step by step explanation of how an std::index_sequence is coded and the meta programming principal in question for each stage. Think really dumbed down :) 回答1: I see sample code around there, but I really want a

问题 I'm investigating a C++11 idiom which might be called "overloaded lambda": http://cpptruths.blogspot.com/2014/05/fun-with-lambdas-c14-style-part-2.html http://martinecker.com/martincodes/lambda-expression-overloading/ Overloading n functions with variadic template seemed very appealing to me but it turned out it didn't work with variable capture: any of [&] [=] [y] [&y] (and [this] etc if in a member function) lead to compilation failure: error: no match for call to '(overload<main(int, char*

问题 Gcc and clang seem to disagree on whether this code should compile or not: #include <type_traits> template <typename Signature, int N = 0> struct MyDelegate { }; template <typename D> struct signature_traits; template <template <typename> class Delegate, typename Signature> struct signature_traits<Delegate<Signature>> { using type = Signature; }; static_assert(std::is_same_v< void(int, int), signature_traits<MyDelegate<void(int, int)>>::type >); See godbolt output here and try it. I'm siding

问题 In our code we have the following class: template<class A, class B> class myClass { typedef std::list<Object<A,B>> MyList; typedef std::map<A, typename mList::iterator> MyMap MyList mList; MyMap mMap; } class A is metaprogrammed and it can be a string, int and so on. I would like to change the code so in case class A is a "meta string" a map will be used, otherwise unordered_map will be used. I've tried to add some more meta programming but haven't succeeded yet: template< class A, class B>

问题 I have a header file, which I can control its contents. Additionally I have an interface I1 (defined in some other file) from which various implementations derived. I want to prohibit those implementations from including this header file. So that during compile time if the file is included the compilation will fail, otherwise it will continue as usual. So I have header file and an interface definition (in some other file). I want to prohibit interface implementations from including the given