v3/algorithm/for_each_n.hpp

0001 /// \file
0002 // Range v3 library
0003 //
0004 //  Copyright Eric Niebler 2014-present
0005 //  Copyright Rostislav Khlebnikov 2017
0006 //
0007 //  Use, modification and distribution is subject to the
0008 //  Boost Software License, Version 1.0. (See accompanying
0009 //  file LICENSE_1_0.txt or copy at
0010 //  http://www.boost.org/LICENSE_1_0.txt)
0011 //
0012 // Project home: https://github.com/ericniebler/range-v3
0013 //
0014 #ifndef RANGES_V3_ALGORITHM_FOR_EACH_N_HPP
0015 #define RANGES_V3_ALGORITHM_FOR_EACH_N_HPP
0016
0017 #include <functional>
0018
0019 #include <range/v3/range_fwd.hpp>
0020
0021 #include <range/v3/algorithm/result_types.hpp>
0022 #include <range/v3/functional/identity.hpp>
0023 #include <range/v3/functional/invoke.hpp>
0024 #include <range/v3/iterator/operations.hpp>
0025 #include <range/v3/iterator/traits.hpp>
0026 #include <range/v3/range/concepts.hpp>
0027 #include <range/v3/range/dangling.hpp>
0028 #include <range/v3/range/traits.hpp>
0029 #include <range/v3/utility/static_const.hpp>
0030
0031 #include <range/v3/detail/prologue.hpp>
0032
0033 namespace ranges
0034 {
0035     /// \addtogroup group-algorithms
0036     /// @{
0037     RANGES_FUNC_BEGIN(for_each_n)
0038
0039         /// \brief function template \c for_each_n
0040         template(typename I, typename F, typename P = identity)(
0041             requires input_iterator<I> AND
0042                 indirectly_unary_invocable<F, projected<I, P>>)
0043         constexpr I RANGES_FUNC(for_each_n)(I first, iter_difference_t<I> n, F fun, P proj = P{})
0044         {
0045             RANGES_EXPECT(0 <= n);
0046             auto norig = n;
0047             auto b = uncounted(first);
0048             for(; 0 < n; ++b, --n)
0049                 invoke(fun, invoke(proj, *b));
0050             return recounted(first, b, norig);
0051         }
0052
0053         /// \overload
0054         template(typename Rng, typename F, typename P = identity)(
0055             requires input_range<Rng> AND
0056                 indirectly_unary_invocable<F, projected<iterator_t<Rng>, P>>)
0057         constexpr borrowed_iterator_t<Rng> RANGES_FUNC(for_each_n)(
0058             Rng && rng, range_difference_t<Rng> n, F fun, P proj = P{})
0059         {
0060             if(sized_range<Rng>)
0061                 RANGES_EXPECT(n <= distance(rng));
0062
0063             return (*this)(begin(rng), n, detail::move(fun), detail::move(proj));
0064         }
0065
0066     RANGES_FUNC_END(for_each_n)
0067
0068     namespace cpp20
0069     {
0070         using ranges::for_each_n;
0071     }
0072     /// @}
0073 } // namespace ranges
0074
0075 #include <range/v3/detail/epilogue.hpp>
0076
0077 #endif