#include <iostream>
#include <utility>
 
 
 
template<typename T>
constexpr const T& mirror(const T& t)
{
	return t;
}
 
template<class A, class B>
constexpr auto mirror(const std::pair<A, B>& p)
{
	return std::make_pair(mirror(p.second), mirror(p.first));
}
 
int main() {
	constexpr std::pair<int, float> a{42, 4.2f};
 
	static_assert(std::make_pair(4.2f, 42) == mirror(a), "unexpected");
 
	constexpr std::pair<int, std::pair<float, char>> b{0, {4.2f, '*'}};
 
	static_assert(std::make_pair(std::make_pair('*', 4.2f), 0) == mirror(b), "unexpected");
}

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