v3/algorithm/count.hpp

0001 /// \file
0002 // Range v3 library
0003 //
0004 //  Copyright Eric Niebler 2014-present
0005 //
0006 //  Use, modification and distribution is subject to the
0007 //  Boost Software License, Version 1.0. (See accompanying
0008 //  file LICENSE_1_0.txt or copy at
0009 //  http://www.boost.org/LICENSE_1_0.txt)
0010 //
0011 // Project home: https://github.com/ericniebler/range-v3
0012 //
0013 #ifndef RANGES_V3_ALGORITHM_COUNT_HPP
0014 #define RANGES_V3_ALGORITHM_COUNT_HPP
0015
0016 #include <utility>
0017
0018 #include <range/v3/range_fwd.hpp>
0019
0020 #include <range/v3/functional/identity.hpp>
0021 #include <range/v3/functional/invoke.hpp>
0022 #include <range/v3/iterator/concepts.hpp>
0023 #include <range/v3/iterator/traits.hpp>
0024 #include <range/v3/range/access.hpp>
0025 #include <range/v3/range/concepts.hpp>
0026 #include <range/v3/range/traits.hpp>
0027 #include <range/v3/utility/static_const.hpp>
0028
0029 #include <range/v3/detail/prologue.hpp>
0030
0031 namespace ranges
0032 {
0033     /// \addtogroup group-algorithms
0034     /// @{
0035     RANGES_FUNC_BEGIN(count)
0036
0037         /// \brief function template \c count
0038         template(typename I, typename S, typename V, typename P = identity)(
0039             requires input_iterator<I> AND sentinel_for<S, I> AND
0040             indirect_relation<equal_to, projected<I, P>, V const *>)
0041         constexpr iter_difference_t<I> //
0042         RANGES_FUNC(count)(I first, S last, V const & val, P proj = P{})
0043         {
0044             iter_difference_t<I> n = 0;
0045             for(; first != last; ++first)
0046                 if(invoke(proj, *first) == val)
0047                     ++n;
0048             return n;
0049         }
0050
0051         /// \overload
0052         template(typename Rng, typename V, typename P = identity)(
0053             requires input_range<Rng> AND
0054             indirect_relation<equal_to, projected<iterator_t<Rng>, P>, V const *>)
0055         constexpr iter_difference_t<iterator_t<Rng>> //
0056         RANGES_FUNC(count)(Rng && rng, V const & val, P proj = P{})
0057         {
0058             return (*this)(begin(rng), end(rng), val, std::move(proj));
0059         }
0060
0061     RANGES_FUNC_END(count)
0062
0063     namespace cpp20
0064     {
0065         using ranges::count;
0066     }
0067     /// @}
0068 } // namespace ranges
0069
0070 #include <range/v3/detail/epilogue.hpp>
0071
0072 #endif