Horizon
count_if.hpp
Go to the documentation of this file.
1 // Range v3 library
3 //
4 // Copyright Eric Niebler 2014-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 #ifndef RANGES_V3_ALGORITHM_COUNT_IF_HPP
14 #define RANGES_V3_ALGORITHM_COUNT_IF_HPP
15 
16 #include <utility>
17 
18 #include <range/v3/range_fwd.hpp>
19 
27 #include <range/v3/utility/static_const.hpp>
28 
29 #include <range/v3/detail/prologue.hpp>
30 
31 namespace ranges
32 {
35  RANGES_FUNC_BEGIN(count_if)
36 
37 
38  template(typename I, typename S, typename R, typename P = identity)(
39  requires input_iterator<I> AND sentinel_for<S, I> AND
40  indirect_unary_predicate<R, projected<I, P>>)
41  constexpr iter_difference_t<I> RANGES_FUNC(count_if)(I first, S last, R pred, P proj = P{})
42  {
43  iter_difference_t<I> n = 0;
44  for(; first != last; ++first)
45  if(invoke(pred, invoke(proj, *first)))
46  ++n;
47  return n;
48  }
49 
51  template(typename Rng, typename R, typename P = identity)(
52  requires input_range<Rng> AND
53  indirect_unary_predicate<R, projected<iterator_t<Rng>, P>>)
54  constexpr iter_difference_t<iterator_t<Rng>> //
55  RANGES_FUNC(count_if)(Rng && rng, R pred, P proj = P{})
56  {
57  return (*this)(begin(rng), end(rng), std::move(pred), std::move(proj));
58  }
59 
60  RANGES_FUNC_END(count_if)
61 
62  namespace cpp20
63  {
64  using ranges::count_if;
65  }
67 } // namespace ranges
68 
69 #include <range/v3/detail/epilogue.hpp>
70 
71 #endif
template(typename Rng, typename R, typename P=identity)(requires input_range< Rng > AND indirect_unary_predicate< R
This is an overloaded member function, provided for convenience. It differs from the above function o...
CPP_concept sentinel_for
\concept sentinel_for
Definition: concepts.hpp:306
CPP_concept indirect_unary_predicate
\concept indirect_unary_predicate
Definition: concepts.hpp:632
CPP_concept input_iterator
\concept input_iterator
Definition: concepts.hpp:362
decltype(begin(declval(Rng &))) iterator_t
Definition: access.hpp:698
typename Fn::template invoke< Args... > invoke
Evaluate the invocable Fn with the arguments Args.
Definition: meta.hpp:541
front< Pair > first
Retrieve the first element of the pair Pair.
Definition: meta.hpp:2251
Definition: identity.hpp:25