accumulate.hpp

/// \file
// Range v3 library
//
//  Copyright Eric Niebler 2013-present
//
//  Use, modification and distribution is subject to 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)
//
// Project home: https://github.com/ericniebler/range-v3
//
#ifndef RANGES_V3_NUMERIC_ACCUMULATE_HPP
#define RANGES_V3_NUMERIC_ACCUMULATE_HPP

#include <meta/meta.hpp>
#include <range/v3/begin_end.hpp>
#include <range/v3/range_traits.hpp>
#include <range/v3/range_concepts.hpp>
#include <range/v3/utility/functional.hpp>
#include <range/v3/utility/iterator_traits.hpp>
#include <range/v3/utility/iterator_concepts.hpp>
#include <range/v3/utility/static_const.hpp>

namespace ranges
{
    inline namespace v3
    {
        template<typename I, typename T, typename Op = plus, typename P = ident>
        using Accumulateable = meta::strict_and<
            InputIterator<I>,
            IndirectInvocable<Op, T *, projected<I, P>>,
            Assignable<T&, indirect_invoke_result_t<Op &, T *, projected<I, P>>>>;

        struct accumulate_fn
        {
            template<typename I, typename S, typename T, typename Op = plus, typename P = ident,
                CONCEPT_REQUIRES_(Sentinel<S, I>() && Accumulateable<I, T, Op, P>())>
            T operator()(I begin, S end, T init, Op op = Op{}, P proj = P{}) const
            {
                for(; begin != end; ++begin)
                    init = invoke(op, init, invoke(proj, *begin));
                return init;
            }

            template<typename Rng, typename T, typename Op = plus, typename P = ident,
                typename I = iterator_t<Rng>,
                CONCEPT_REQUIRES_(Range<Rng>() && Accumulateable<I, T, Op, P>())>
            T operator()(Rng && rng, T init, Op op = Op{}, P proj = P{}) const
            {
                return (*this)(begin(rng), end(rng), std::move(init), std::move(op),
                    std::move(proj));
            }
        };

        RANGES_INLINE_VARIABLE(with_braced_init_args<accumulate_fn>, accumulate)
    }
}

#endif