identity_element.hpp

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/*
    Copyright 2013 Adobe
    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)
*/
/**************************************************************************************************/
 
#ifndef ADOBE_ALGORITHM_IDENTITY_ELEMENT_HPP
#define ADOBE_ALGORITHM_IDENTITY_ELEMENT_HPP
 
#include <adobe/config.hpp>
 
#include <algorithm>
#include <functional>
 
/**************************************************************************************************/
 
namespace adobe {
 
/**************************************************************************************************/
template <typename Op>
struct identity_element {
    typedef typename Op::result_type result_type;

    result_type operator()() const;
};

template <typename T>
struct identity_element<std::plus<T>> {
    typedef T result_type;

    result_type operator()() const { return T(0); }
};

template <typename T>
struct identity_element<std::multiplies<T>> {
    typedef T result_type;

    result_type operator()() const { return T(1); }
};
 
/**************************************************************************************************/
 
} // namespace adobe
 
/**************************************************************************************************/
 
#endif
 
/**************************************************************************************************/