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#pragma once
#include <algorithm> // IWYU pragma: keep
#include <array>
#include <cstddef>
#include <memory>
#include <tuple>
template<typename T, std::size_t N>
constexpr auto
transform_array(const std::array<T, N> & in, auto && transform)
{
std::array<decltype(transform(in.front())), N> out {};
std::transform(in.begin(), in.end(), out.begin(), transform);
return out;
}
namespace {
template<size_t... N> struct GetNth {
decltype(auto)
operator()(const auto & tup) const
{
if constexpr (sizeof...(N) == 1) {
return std::get<N...>(tup);
}
else {
return std::tie(std::get<N>(tup)...);
}
}
};
}
template<size_t... N> inline constexpr auto Nth = GetNth<N...> {};
inline constexpr auto GetFirst = Nth<0>;
inline constexpr auto GetSecond = Nth<1>;
inline constexpr auto GetSwapped = Nth<0, 1>;
template<typename T, typename M> struct Decompose {
consteval Decompose(M T::*) { }
using ValueType = M;
using ContainerType = T;
};
template<auto MbrPtr> using MemberValueType = typename decltype(Decompose {MbrPtr})::ValueType;
template<auto MbrPtr> using ContainerType = typename decltype(Decompose {MbrPtr})::ContainerType;
template<typename T>
bool
createIfRequired(std::shared_ptr<T> & instance, std::weak_ptr<T> & common)
{
if (!instance && !(instance = common.lock())) {
common = instance = std::make_shared<T>();
return true;
}
return false;
}
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