C + + void_t

Source: Internet
Author: User

Consider the following code:

#include <type_traits>#include<iostream>#include<vector>using namespacestd;template<typename T, TypeName =void>structRangeconcept:std::false_type {};template<typename t>structrangeconcept<T, std::void_t<decltype (std::d eclval<t >(). Begin ()), Decltype (std::d eclval<t >(). End ())> >: std::true_type {};template<typename cont>voidShow (Cont c) {Static_assert (rangeconcept< Cont >::value,"must be a range. Means: it has begin () and end ()" );}
int Main () {std::vector<int> vec{1,2,3,4,5 }; Show (VEC); }

This is the void_t artifact brought by c++17. Writing a static assertion is incredibly easy. A handwritten concept check is no longer a patent for C + + library developers.

Reference: http://en.cppreference.com/w/cpp/types/void_t

C + + void_t

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