identity.hpp

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// SPDX-License-Identifier: BSD-2-Clause
 
#ifndef pRC_CORE_BASIC_IDENTITY_H
#define pRC_CORE_BASIC_IDENTITY_H
 
#include <prc/core/basic/concepts.hpp>
 
namespace pRC
{
    template<class T = Void>
    struct Identity;
 
    template<class T>
    struct Identity<T const> : Identity<T>
    {
    };
 
    template<IsVoid T>
    struct Identity<T>
    {
        template<class F>
            requires IsBool<F> || IsIntegral<F>
        constexpr operator F() const
        {
            return Identity<F>()();
        }
    };
 
    template<IsBool T>
    struct Identity<T>
    {
        constexpr T operator()() const
        {
            return true;
        }
 
        template<class X>
            requires IsConstructible<T, X>
        constexpr T operator()(X &&value) const
        {
            return forward<X>(value);
        }
    };
 
    template<IsIntegral T>
    struct Identity<T>
    {
        constexpr T operator()() const
        {
            return 1;
        }
 
        template<class X>
            requires IsConstructible<T, X>
        constexpr T operator()(X &&value) const
        {
            return forward<X>(value);
        }
    };
}
#endif // pRC_CORE_BASIC_IDENTITY_H