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c++templatesmetaprogrammingtemplate-specialization

How to know if a type is a specialization of std::vector?


I've been on this problem all morning with no result whatsoever. Basically, I need a simple metaprogramming thing that allows me to branch to different specializations if the parameter passed is a kind of std::vector or not.

Some kind of is_base_of for templates.

Does such a thing exist ?


Solution

  • In C++11 you can also do it in a more generic way:

    #include <type_traits>
    #include <iostream>
    #include <vector>
    #include <list>
    
    template<typename Test, template<typename...> class Ref>
    struct is_specialization : std::false_type {};
    
    template<template<typename...> class Ref, typename... Args>
    struct is_specialization<Ref<Args...>, Ref>: std::true_type {};
    
    
    int main()
    {
        typedef std::vector<int> vec;
        typedef int not_vec;
        std::cout << is_specialization<vec, std::vector>::value << is_specialization<not_vec, std::vector>::value;
    
        typedef std::list<int> lst;
        typedef int not_lst;
        std::cout << is_specialization<lst, std::list>::value << is_specialization<not_lst, std::list>::value;
    }