undefined.h

 
//          Copyright John McFarlane 2018.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file ../LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)
 
#if !defined(CNL_IMPL_OVERFLOW_UNDEFINED_H)
#define CNL_IMPL_OVERFLOW_UNDEFINED_H
 
#include "../custom_operator/homogeneous_operator_tag_base.h"
#include "../polarity.h"
#include "../unreachable.h"
#include "is_overflow_tag.h"
#include "is_tag.h"
#include "overflow_operator.h"
 
namespace cnl {
    struct undefined_overflow_tag
        : _impl::homogeneous_deduction_tag_base
        , _impl::homogeneous_operator_tag_base {
    };
 
    namespace _impl {
        template<>
        struct is_overflow_tag<undefined_overflow_tag> : std::true_type {
        };
 
        template<typename Operator>
        struct overflow_operator<Operator, undefined_overflow_tag, polarity::positive> {
            template<typename Destination, typename Source>
            [[nodiscard]] constexpr auto operator()(Source const&) const
            {
                return unreachable<Destination>("positive overflow");
            }
 
            template<class... Operands>
            [[nodiscard]] constexpr auto operator()(
                    Operands const&...) const
            {
                return unreachable<op_result<Operator, Operands...>>("positive overflow");
            }
        };
 
        template<typename Operator>
        struct overflow_operator<Operator, undefined_overflow_tag, polarity::negative> {
            template<typename Destination, typename Source>
            [[nodiscard]] constexpr auto operator()(Source const&) const
            {
                return unreachable<Destination>("negative overflow");
            }
 
            template<class... Operands>
            [[nodiscard]] constexpr auto operator()(
                    Operands const&...) const
            {
                return unreachable<op_result<Operator, Operands...>>("negative overflow");
            }
        };
    }
}
 
#endif  // CNL_IMPL_OVERFLOW_UNDEFINED_H