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count.hpp
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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_HPP
14 #define RANGES_V3_ALGORITHM_COUNT_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)
36 
37 
38  template(typename I, typename S, typename V, typename P = identity)(
39  requires input_iterator<I> AND sentinel_for<S, I> AND
40  indirect_relation<equal_to, projected<I, P>, V const *>)
41  constexpr iter_difference_t<I> //
42  RANGES_FUNC(count)(I first, S last, V const & val, P proj = P{})
43  {
44  iter_difference_t<I> n = 0;
45  for(; first != last; ++first)
46  if(invoke(proj, *first) == val)
47  ++n;
48  return n;
49  }
50 
52  template(typename Rng, typename V, typename P = identity)(
53  requires input_range<Rng> AND
54  indirect_relation<equal_to, projected<iterator_t<Rng>, P>, V const *>)
55  constexpr iter_difference_t<iterator_t<Rng>> //
56  RANGES_FUNC(count)(Rng && rng, V const & val, P proj = P{})
57  {
58  return (*this)(begin(rng), end(rng), val, std::move(proj));
59  }
60 
61  RANGES_FUNC_END(count)
62 
63  namespace cpp20
64  {
65  using ranges::count;
66  }
68 } // namespace ranges
69 
70 #include <range/v3/detail/epilogue.hpp>
71 
72 #endif
template(typename Rng, typename V, typename P=identity)(requires input_range< Rng > AND indirect_relation< equal_to
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 input_iterator
\concept input_iterator
Definition: concepts.hpp:362
CPP_concept indirect_relation
\concept indirect_relation
Definition: concepts.hpp:670
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: comparisons.hpp:28
Definition: identity.hpp:25