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
  //
  //===----------------------------------------------------------------------===//
  
  // <forward_list>
  
  // template <class Predicate> void      remove_if(Predicate pred); // C++17 and before
  // template <class Predicate> size_type remove_if(Predicate pred); // C++20 and after
  
  #include <forward_list.hxx>
  #include <iterator.hxx>
  #include <cassert.hxx>
  #include <cstddef.hxx>
  
  #include "test_macros.h"
  #include "min_allocator.h"
  #include "counting_predicates.h"
  
  
  template <class L, class Predicate>
  void do_remove_if(L &l, Predicate pred, typename L::size_type expected)
  {
      typename L::size_type old_size = std::distance(l.begin(), l.end());
  #if TEST_STD_VER > 17
      ASSERT_SAME_TYPE(decltype(l.remove_if(pred)), typename L::size_type);
      assert(l.remove_if(pred) == expected);
  #else
      ASSERT_SAME_TYPE(decltype(l.remove_if(pred)), void);
      l.remove_if(pred);
  #endif
      assert(old_size - std::distance(l.begin(), l.end()) == expected);
  }
  
  bool g(int i)
  {
      return i < 3;
  }
  
  struct PredLWG526 {
      PredLWG526 (int i) : i_(i) {};
      ~PredLWG526() { i_ = -32767; }
      bool operator() (const PredLWG526 &p) const { return p.i_ == i_; }
  
      bool operator==(int i) const { return i == i_;}
      int i_;
  };
  
  int main(int, char**)
  {
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T> C;
          const T t1[] = {0, 5, 5, 0, 0, 0, 5};
          const T t2[] = {5, 5, 5};
          C c1(std::begin(t1), std::end(t1));
          C c2(std::begin(t2), std::end(t2));
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 4);
          assert(c1 == c2);
          assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
      }
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T> C;
          const T t1[] = {0, 0, 0, 0};
          C c1(std::begin(t1), std::end(t1));
          C c2;
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 4);
          assert(c1 == c2);
          assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
      }
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T> C;
          const T t1[] = {5, 5, 5};
          const T t2[] = {5, 5, 5};
          C c1(std::begin(t1), std::end(t1));
          C c2(std::begin(t2), std::end(t2));
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 0);
          assert(c1 == c2);
          assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
      }
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T> C;
          C c1;
          C c2;
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 0);
          assert(c1 == c2);
          assert(cp.count() == 0);
      }
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T> C;
          const T t1[] = {5, 5, 5, 0};
          const T t2[] = {5, 5, 5};
          C c1(std::begin(t1), std::end(t1));
          C c2(std::begin(t2), std::end(t2));
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 1);
          assert(c1 == c2);
          assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
      }
  
      { // LWG issue #526
      int a1[] = {1, 2, 1, 3, 5, 8, 11};
      int a2[] = {   2,    3, 5, 8, 11};
      std::forward_list<PredLWG526> c(a1, a1 + 7);
      do_remove_if(c, std::ref(c.front()), 2);
      for (size_t i = 0; i < 5; ++i)
      {
          assert(!c.empty());
          assert(c.front() == a2[i]);
          c.pop_front();
      }
      assert(c.empty());
      }
  
  #if TEST_STD_VER >= 11
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T, min_allocator<T>> C;
          const T t1[] = {0, 5, 5, 0, 0, 0, 5};
          const T t2[] = {5, 5, 5};
          C c1(std::begin(t1), std::end(t1));
          C c2(std::begin(t2), std::end(t2));
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 4);
          assert(c1 == c2);
          assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
      }
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T, min_allocator<T>> C;
          const T t1[] = {0, 0, 0, 0};
          C c1(std::begin(t1), std::end(t1));
          C c2;
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 4);
          assert(c1 == c2);
          assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
      }
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T, min_allocator<T>> C;
          const T t1[] = {5, 5, 5};
          const T t2[] = {5, 5, 5};
          C c1(std::begin(t1), std::end(t1));
          C c2(std::begin(t2), std::end(t2));
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 0);
          assert(c1 == c2);
          assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
      }
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T, min_allocator<T>> C;
          C c1;
          C c2;
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 0);
          assert(c1 == c2);
          assert(cp.count() == 0);
      }
      {
          typedef int T;
          typedef unary_counting_predicate<bool(*)(T), T> Predicate;
          typedef std::forward_list<T, min_allocator<T>> C;
          const T t1[] = {5, 5, 5, 0};
          const T t2[] = {5, 5, 5};
          C c1(std::begin(t1), std::end(t1));
          C c2(std::begin(t2), std::end(t2));
          Predicate cp(g);
          do_remove_if(c1, std::ref(cp), 1);
          assert(c1 == c2);
          assert(cp.count() == static_cast<std::size_t>(std::distance(std::begin(t1), std::end(t1))));
      }
  #endif
  
    return 0;
  }
  