text: //===----------------------------------------------------------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  // <algorithm>
  
  // template<InputIterator Iter, Predicate<auto, Iter::value_type> Pred>
  //   requires CopyConstructible<Pred>
  //   constexpr Iter::difference_type   // constexpr after C++17
  //   count_if(Iter first, Iter last, Pred pred);
  
  #include <algorithm>
  #include <functional>
  #include <cassert>
  
  #include "test_macros.h"
  #include "test_iterators.h"
  
  struct eq {
      TEST_CONSTEXPR eq (int val) : v(val) {}
      TEST_CONSTEXPR bool operator () (int v2) const { return v == v2; }
      int v;
      };
  
  #if TEST_STD_VER > 17
  TEST_CONSTEXPR bool test_constexpr() {
      int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
      int ib[] = {1, 2, 3, 4, 5, 6};
      return    (std::count_if(std::begin(ia), std::end(ia), eq(2)) == 3)
             && (std::count_if(std::begin(ib), std::end(ib), eq(9)) == 0)
             ;
      }
  #endif
  
  int main(int, char**)
  {
      int ia[] = {0, 1, 2, 2, 0, 1, 2, 3};
      const unsigned sa = sizeof(ia)/sizeof(ia[0]);
      assert(std::count_if(input_iterator<const int*>(ia),
                           input_iterator<const int*>(ia + sa),
                           eq(2)) == 3);
      assert(std::count_if(input_iterator<const int*>(ia),
                           input_iterator<const int*>(ia + sa),
                           eq(7)) == 0);
      assert(std::count_if(input_iterator<const int*>(ia),
                           input_iterator<const int*>(ia),
                           eq(2)) == 0);
  
  #if TEST_STD_VER > 17
      static_assert(test_constexpr());
  #endif
  
    return 0;
  }
  