namespace std {
template<class I1, class I2 = I1>
concept indirectly_swappable =
indirectly_readable<I1> && indirectly_readable<I2> &&
requires(const I1 i1, const I2 i2) {
ranges::iter_swap(i1, i1);
ranges::iter_swap(i2, i2);
ranges::iter_swap(i1, i2);
ranges::iter_swap(i2, i1);
};
}
概要
indirectly_swappableは、indirectly_readableな型I1, I2の参照する要素のオブジェクトがswap可能であることを表すコンセプトである。
単純には、型I1, I2のオブジェクトをそれぞれi1, i2とするとstd::ranges::swap(*i1, *i2)のような交換操作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 I1, typename I2>
requires std::indirectly_swappable<I1, I2>
void f(const char* nameI1, const char* nameI2) {
std::cout << nameI1 << " is indirectly_swappable " << nameI2 << std::endl;
}
template<typename I1, typename I2>
void f(const char* nameI1, const char* nameI2) {
std::cout << nameI1 << " is not indirectly_swappable " << nameI2 << 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>");
std::cout << "\n";
f<int*, const int*>("int*", "const 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*");
}
xxxxxxxxxx#include <iostream>#include <concepts>#include <iterator>#include <vector>#include <memory>template<typename I1, typename I2> requires std::indirectly_swappable<I1, I2>void f(const char* nameI1, const char* nameI2) { std::cout << nameI1 << " is indirectly_swappable " << nameI2 << std::endl;}template<typename I1, typename I2>void f(const char* nameI1, const char* nameI2) { std::cout << nameI1 << " is not indirectly_swappable " << nameI2 << 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>"); std::cout << "\n"; f<int*, const int*>("int*", "const 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*");}出力
int* is indirectly_swappable int* const
std::unique_ptr<int> is indirectly_swappable int*
std::vector<int>::iterator is indirectly_swappable std::unique_ptr<int>
int* is not indirectly_swappable const int*
std::istream_iterator<int> is not indirectly_swappable std::vector<int>::iterator
std::istream_iterator<int> is not indirectly_swappable std::ostream_iterator<int>
del_copy_ctor* is not indirectly_swappable del_copy_ctor*
バージョン
言語
- C++20
処理系
- Clang: ??
- GCC: 10.1 ✅
- Visual C++: 2019 Update 6 ✅