ObjectConcepts.hpp

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#pragma once
#include <ostream>
#include <concepts>
 
namespace fishnet::util {
template<typename T>
concept HasToString = requires(const T &obj){
    { obj.toString() } -> std::convertible_to<std::string>;
};
 
template<typename T>
concept HasHashMethod = requires(const std::remove_cvref_t<T> & obj){
    {obj.hash()} -> std::convertible_to<std::size_t>;
};
 
template<typename Key>
concept Hashable = HasHashMethod<Key> || requires(Key key)
{
    { std::hash<std::remove_cvref_t<Key>>{}(key) } -> std::convertible_to<std::size_t>;
};
 
template<typename T>
concept Mapable = Hashable<T> && std::equality_comparable<T>;
 
template<typename T>
concept Object = HasToString<T> && Hashable<T> && std::equality_comparable<T>;
 
} // fishnet::util
 
namespace std{
    template<fishnet::util::HasHashMethod T>
    struct hash<T>{
        size_t operator()(const fishnet::util::HasHashMethod auto & obj) const {
            return obj.hash();
        }
    };
}
 
constexpr std::ostream & operator << (std::ostream & os,fishnet::util::HasToString auto const & obj) noexcept{
    os << obj.toString();
    return os;
}