Mercurial > lbo > hg > ctmp
view src/replace_type.cc @ 3:58777a883f54
Vastly improve replace_type
author | Lewin Bormann <lbo@spheniscida.de> |
---|---|
date | Wed, 25 Mar 2020 10:10:30 +0100 |
parents | 20c6c0bec02a |
children | cc90585713b4 |
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#include <iostream> #include <type_traits> template<typename C, typename X, typename Y> struct replace_type { typedef C type; }; // Simple replacement. template<typename X, typename Y> struct replace_type<X, X, Y> { typedef Y type; }; namespace { // For pointer/reference types, if C* == X, replace, otherwise continue replacing. template<bool is_same, typename C, typename X, typename Y> struct replace_type_ptr_helper { typedef Y type; }; template<typename C, typename X, typename Y> struct replace_type_ptr_helper<true, C*, X, Y> { typedef Y type; }; template<typename C, typename X, typename Y> struct replace_type_ptr_helper<false, C*, X, Y> { typedef typename replace_type<C, X, Y>::type* type; }; template<typename C, typename X, typename Y> struct replace_type_ptr_helper<true, C&, X, Y> { typedef Y type; }; template<typename C, typename X, typename Y> struct replace_type_ptr_helper<false, C&, X, Y> { typedef typename replace_type<C, X, Y>::type& type; }; template<typename C, typename X, typename Y> struct replace_type_ptr_helper<true, C&&, X, Y> { typedef Y type; }; template<typename C, typename X, typename Y> struct replace_type_ptr_helper<false, C&&, X, Y> { typedef typename replace_type<C, X, Y>::type&& type; }; } template<typename C, typename X, typename Y> struct replace_type<C*, X, Y> { typedef typename replace_type_ptr_helper<std::is_same<C*, X>::value, C*, X, Y>::type type; }; template<typename C, typename X, typename Y> struct replace_type<C&, X, Y> { typedef typename replace_type_ptr_helper<std::is_same<C&, X>::value, C&, X, Y>::type type; }; template<typename C, typename X, typename Y> struct replace_type<C&&, X, Y> { typedef typename replace_type_ptr_helper<std::is_same<C&&, X>::value, C&&, X, Y>::type type; }; template<typename C, typename X, typename Y> struct replace_type<const C, X, Y> { typedef const typename replace_type_ptr_helper<std::is_same<const C, X>::value, const C, X, Y>::type type; }; template<typename R, typename A, typename X, typename Y> struct replace_type<R (*)(A), X, Y> { typedef typename replace_type<R, X, Y>::type (*type)(typename replace_type<A, X, Y>::type); }; int main(void) { typedef const long long* typ; std::cout << typeid(typ).name() << std::endl; std::cout << typeid(replace_type<typ, long long, unsigned>::type).name() << std::endl; return 0; }