applicative.h

Go to the documentation of this file.

/**********************************************************************
 * LeechCraft - modular cross-platform feature rich internet client.
 * Copyright (C) 2006-2014  Georg Rudoy
 *
 * Boost Software License - Version 1.0 - August 17th, 2003
 *
 * Permission is hereby granted, free of charge, to any person or organization
 * obtaining a copy of the software and accompanying documentation covered by
 * this license (the "Software") to use, reproduce, display, distribute,
 * execute, and transmit the Software, and to prepare derivative works of the
 * Software, and to permit third-parties to whom the Software is furnished to
 * do so, all subject to the following:
 *
 * The copyright notices in the Software and this entire statement, including
 * the above license grant, this restriction and the following disclaimer,
 * must be included in all copies of the Software, in whole or in part, and
 * all derivative works of the Software, unless such copies or derivative
 * works are solely in the form of machine-executable object code generated by
 * a source language processor.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
 * SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
 * FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 **********************************************************************/
 
#pragma once
 
#include <optional>
#include <boost/optional.hpp>
 
namespace LC
{
namespace Util
{
    template<typename Applicative>
    struct InstanceApplicative;
 
    template<typename AF, typename AV>
    using GSLResult_t = typename InstanceApplicative<AF>::template GSLResult<AV>::Type_t;
 
    template<template<typename...> class Applicative, typename... Args, typename T>
    auto Pure (const T& v)
    {
        return InstanceApplicative<Applicative<Args..., T>>::Pure (v);
    }
 
    template<typename Applicative, typename T>
    auto Pure (const T& v) -> decltype (InstanceApplicative<Applicative>::Pure (v))
    {
        return InstanceApplicative<Applicative>::Pure (v);
    }
 
    template<typename AF, typename AV>
    GSLResult_t<AF, AV> GSL (const AF& af, const AV& av)
    {
        return InstanceApplicative<AF>::GSL (af, av);
    }
 
    template<typename AF, typename AV>
    auto operator* (const AF& af, const AV& av) -> decltype (GSL (af, av))
    {
        return GSL (af, av);
    }
 
    // Implementations
    template<typename T>
    struct InstanceApplicative<boost::optional<T>>
    {
        using Type_t = boost::optional<T>;
 
        template<typename>
        struct GSLResult;
 
        template<typename V>
        struct GSLResult<boost::optional<V>>
        {
            using Type_t = boost::optional<std::result_of_t<T (const V&)>>;
        };
 
        template<typename U>
        static boost::optional<U> Pure (const U& v)
        {
            return { v };
        }
 
        template<typename AV>
        static GSLResult_t<Type_t, AV> GSL (const Type_t& f, const AV& v)
        {
            if (!f || !v)
                return {};
 
            return { (*f) (*v) };
        }
    };
 
    template<typename T>
    struct InstanceApplicative<std::optional<T>>
    {
        using Type_t = std::optional<T>;
 
        template<typename>
        struct GSLResult;
 
        template<typename V>
        struct GSLResult<std::optional<V>>
        {
            using Type_t = std::optional<std::result_of_t<T (const V&)>>;
        };
 
        template<typename U>
        static std::optional<U> Pure (const U& v)
        {
            return { v };
        }
 
        template<typename AV>
        static GSLResult_t<Type_t, AV> GSL (const Type_t& f, const AV& v)
        {
            if (!f || !v)
                return {};
 
            return { (*f) (*v) };
        }
    };
}
}