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take.hpp
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1 // Range v3 library
3 //
4 // Copyright Eric Niebler 2013-present
5 //
6 // Use, modification and distribution is subject to the
7 // Boost Software License, Version 1.0. (See accompanying
8 // file LICENSE_1_0.txt or copy at
9 // http://www.boost.org/LICENSE_1_0.txt)
10 //
11 // Project home: https://github.com/ericniebler/range-v3
12 //
13 
14 #ifndef RANGES_V3_ACTION_TAKE_HPP
15 #define RANGES_V3_ACTION_TAKE_HPP
16 
17 #include <range/v3/range_fwd.hpp>
18 
25 #include <range/v3/utility/static_const.hpp>
26 
27 #include <range/v3/detail/prologue.hpp>
28 
29 namespace ranges
30 {
33  namespace actions
34  {
35  struct take_fn
36  {
37  template(typename Int)(
38  requires detail::integer_like_<Int>)
39  constexpr auto operator()(Int n) const
40  {
41  return make_action_closure(bind_back(take_fn{}, n));
42  }
43 
44  template(typename Rng)(
45  requires forward_range<Rng> AND
46  erasable_range<Rng &, iterator_t<Rng>, sentinel_t<Rng>>)
47  Rng operator()(Rng && rng, range_difference_t<Rng> n) const
48  {
49  RANGES_EXPECT(n >= 0);
50  ranges::actions::erase(
51  rng, ranges::next(begin(rng), n, end(rng)), end(rng));
52  return static_cast<Rng &&>(rng);
53  }
54  };
55 
58  } // namespace actions
60 } // namespace ranges
61 
62 #include <range/v3/detail/epilogue.hpp>
63 
64 #endif
decltype(begin(declval(Rng &))) iterator_t
Definition: access.hpp:698
RANGES_INLINE_VARIABLE(detail::to_container_fn< detail::from_range< std::vector >>, to_vector) template< template< typename... > class ContT > auto to(RANGES_HIDDEN_DETAIL(detail
For initializing a container of the specified type with the elements of an Range.
Definition: conversion.hpp:399
CPP_concept erasable_range
\concept erasable_range
Definition: erase.hpp:76
defer< bind_back, Fn, Ts... > bind_back
Definition: meta.hpp:994
Definition: take.hpp:36