sign.hpp

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#ifndef EAGINE_MATH_SIGN_HPP
#define EAGINE_MATH_SIGN_HPP
 
#include <type_traits>
 
namespace eagine::math {
//------------------------------------------------------------------------------
template <typename T>
class sign {
public:
    using type = sign;
 
    using value_type = T;
 
    constexpr sign() noexcept = default;
 
    constexpr explicit sign(bool pos) noexcept
      : _positive{pos} {}
 
    template <
      typename X,
      typename = std::enable_if_t<!std::is_same_v<X, sign<T>>>>
    constexpr explicit sign(const X& value) noexcept
      : _positive{value >= X(0)} {}
 
    template <
      typename X,
      typename = std::enable_if_t<!std::is_same_v<X, sign<T>>>>
    auto operator=(const X& value) noexcept -> auto& {
        _positive = (value >= X(0));
        return *this;
    }
 
    static constexpr auto plus() noexcept -> sign {
        return {true};
    }
 
    static constexpr auto minus() noexcept -> sign {
        return {false};
    }
 
    operator T() const noexcept {
        return _positive ? T{1} : T{-1};
    }
 
    auto flip() noexcept -> auto& {
        _positive = !_positive;
        return *this;
    }
 
    auto flipped() const noexcept -> sign {
        return {!_positive};
    }
 
    auto operator-() const noexcept -> sign {
        return flipped();
    }
 
    auto operator!() const noexcept -> sign {
        return flipped();
    }
 
private:
    bool _positive{true};
};
//------------------------------------------------------------------------------
} // namespace eagine::math
 
#endif // EAGINE_MATH_SIGN_HPP