fwd_value.hpp

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//          Copyright Dominic Koepke 2019 - 2023.
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          https://www.boost.org/LICENSE_1_0.txt)
 
#ifndef SL_UTILITY_NULLABLES_FWD_VALUE_HPP
#define SL_UTILITY_NULLABLES_FWD_VALUE_HPP
 
#pragma once
 
#include "Simple-Utility/functional/bind_back.hpp"
#include "Simple-Utility/nullables/base.hpp"
 
namespace sl::nullables::detail
{
    template <input_nullable TInputNullable, std::invocable<dereference_result_t<TInputNullable>> TFunc>
    constexpr void fwd_value(TInputNullable&& inputNullable, TFunc&& func)
    {
        if (inputNullable != null_v<TInputNullable>)
        {
            std::invoke(std::forward<TFunc>(func), unwrap(std::forward<TInputNullable>(inputNullable)));
        }
    }
 
    class fwd_value_caller_fn
    {
    public:
        template <input_nullable TInputNullable, std::invocable<dereference_result_t<TInputNullable>> TFunc>
        constexpr void operator ()
        (
            TInputNullable&& inputNullable,
            TFunc&& func
        ) const
        noexcept(noexcept(fwd_value(std::declval<TInputNullable>(), std::declval<TFunc>())))
        {
            fwd_value(
                std::forward<TInputNullable>(inputNullable),
                std::forward<TFunc>(func)
            );
        }
    };
}
 
namespace sl::nullables
{
    inline constexpr auto fwd_value = []<class Fn>(Fn&& fn) noexcept(std::is_nothrow_constructible_v<std::remove_cvref_t<Fn>, Fn>)
    {
        return Algorithm{functional::bind_back(detail::fwd_value_caller_fn{}, std::forward<Fn>(fn))};
    };
    
}
 
#endif