namespace std {
template<class In, class Out>
concept indirectly_movable =
indirectly_readable<In> &&
indirectly_writable<Out, iter_rvalue_reference_t<In>>;
}
概要
indirectly_movableは、indirectly_readableな型Inからindirectly_writableな型Outへ、その要素のオブジェクトがムーブ可能であることを表すコンセプトである。
単純には、型In, Outのオブジェクトをそれぞれin, outとすると*out = std::move(*in)のような代入が可能であることを表している。
例
#include <iostream>
#include <concepts>
#include <iterator>
#include <vector>
#include <memory>
template<typename In, typename Out>
requires std::indirectly_movable<In, Out>
void f(const char* nameIn, const char* nameO) {
std::cout << nameIn << " is indirectly_movable " << nameO << std::endl;
}
template<typename In, typename Out>
void f(const char* nameIn, const char* nameO) {
std::cout << nameIn << " is not indirectly_movable " << nameO << std::endl;
}
struct del_copy_ctor {
del_copy_ctor(const del_copy_ctor&) = delete;
};
int main() {
f<int*, int* const>("int*", "int* const");
f<std::unique_ptr<int>, int*>("std::unique_ptr<int>", "int*");
f<std::vector<int>::iterator, std::unique_ptr<int>>("std::vector<int>::iterator", "std::unique_ptr<int>");
f<std::istream_iterator<int>, std::vector<int>::iterator>("std::istream_iterator<int>", "std::vector<int>::iterator");
f<std::istream_iterator<int>, std::ostream_iterator<int>>("std::istream_iterator<int>", "std::ostream_iterator<int>");
f<del_copy_ctor*, del_copy_ctor*>("del_copy_ctor*", "del_copy_ctor*");
std::cout << "\n";
f<int*, const int*>("int*", "const int*");
f<std::ostream_iterator<int>, std::istream_iterator<int>>("std::ostream_iterator<int>", "std::istream_iterator<int>");
}
xxxxxxxxxx#include <iostream>#include <concepts>#include <iterator>#include <vector>#include <memory>template<typename In, typename Out> requires std::indirectly_movable<In, Out>void f(const char* nameIn, const char* nameO) { std::cout << nameIn << " is indirectly_movable " << nameO << std::endl;}template<typename In, typename Out>void f(const char* nameIn, const char* nameO) { std::cout << nameIn << " is not indirectly_movable " << nameO << std::endl;}struct del_copy_ctor { del_copy_ctor(const del_copy_ctor&) = delete;};int main() { f<int*, int* const>("int*", "int* const"); f<std::unique_ptr<int>, int*>("std::unique_ptr<int>", "int*"); f<std::vector<int>::iterator, std::unique_ptr<int>>("std::vector<int>::iterator", "std::unique_ptr<int>"); f<std::istream_iterator<int>, std::vector<int>::iterator>("std::istream_iterator<int>", "std::vector<int>::iterator"); f<std::istream_iterator<int>, std::ostream_iterator<int>>("std::istream_iterator<int>", "std::ostream_iterator<int>"); f<del_copy_ctor*, del_copy_ctor*>("del_copy_ctor*", "del_copy_ctor*"); std::cout << "\n"; f<int*, const int*>("int*", "const int*"); f<std::ostream_iterator<int>, std::istream_iterator<int>>("std::ostream_iterator<int>", "std::istream_iterator<int>");}出力
int* is indirectly_movable int* const
std::unique_ptr<int> is indirectly_movable int*
std::vector<int>::iterator is indirectly_movable std::unique_ptr<int>
std::istream_iterator<int> is indirectly_movable std::vector<int>::iterator
std::istream_iterator<int> is indirectly_movable std::ostream_iterator<int>
del_copy_ctor* is indirectly_movable del_copy_ctor*
int* is not indirectly_movable const int*
std::ostream_iterator<int> is not indirectly_movable std::istream_iterator<int>
バージョン
言語
- C++20
処理系
- Clang: ??
- GCC: 10.1 ✅
- Visual C++: 2019 Update 6 ✅