is_subtractable.hpp

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//
//  CeresEngine - A game development framework
//
//  Created by Rogiel Sulzbach.
//  Copyright (c) 2018-2022 Rogiel Sulzbach. All rights reserved.
//
 
#pragma once
 
#include <type_traits>
 
namespace CeresEngine::traits {
 
    template<class T, class = void> struct is_subtractable : std::false_type {};
 
    template<class T>
    struct is_subtractable<T,
        std::void_t<
            // clang-format off
            decltype(std::declval<const std::remove_reference_t<T>&>() - std::declval<const std::remove_reference_t<T>&>())
            // clang-format on
            >> : std::is_integral<decltype(std::declval<const std::remove_reference_t<T>&>() - std::declval<const std::remove_reference_t<T>&>())> {};
 
    template<class T> bool constexpr is_subtractable_v = is_subtractable<T>::value;
 
    template<class T>
    concept subtractable = is_subtractable_v<T>;
 
} // namespace CeresEngine::traits