/// \file
// Range v3 library
//
//  Copyright Eric Niebler 2014
//
//  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_ALGORITHM_COUNT_HPP
#define RANGES_V3_ALGORITHM_COUNT_HPP

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

namespace ranges
{
    inline namespace v3
    {
        /// \addtogroup group-algorithms
        /// @{
        struct count_fn
        {
            template<typename I, typename S, typename V, typename P = ident,
                CONCEPT_REQUIRES_(InputIterator<I>() && Sentinel<S, I>() &&
                    IndirectRelation<equal_to, projected<I, P>, V const *>())>
            difference_type_t<I>
            operator()(I begin, S end, V const & val, P proj = P{}) const
            {
                difference_type_t<I> n = 0;
                for(; begin != end; ++begin)
                    if(invoke(proj, *begin) == val)
                        ++n;
                return n;
            }

            template<typename Rng, typename V, typename P = ident,
                typename I = iterator_t<Rng>,
                CONCEPT_REQUIRES_(InputRange<Rng>() &&
                    IndirectRelation<equal_to, projected<I, P>, V const *>())>
            difference_type_t<I>
            operator()(Rng &&rng, V const & val, P proj = P{}) const
            {
                return (*this)(begin(rng), end(rng), val, std::move(proj));
            }
        };

        /// \sa `count_fn`
        /// \ingroup group-algorithms
      RANGES_INLINE_VARIABLE(with_braced_init_args<with_braced_init_args<count_fn>>,
                               count)
        /// @}
    } // namespace v3
} // namespace ranges

#endif // include guard
