test/std/utilities/function.objects/refwrap/refwrap.helpers/ref_2.pass.cpp

//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

// <functional>

// reference_wrapper

// template <ObjectType T> reference_wrapper<T> ref(reference_wrapper<T> t);

#include <functional>
#include <cassert>

#include "counting_predicates.h"

#include "test_macros.h"

bool is5 ( int i ) { return i == 5; }

template <typename T>
bool call_pred ( T pred ) { return pred(5); }

namespace adl {
  struct A {};
  void ref(A) {}
}

TEST_CONSTEXPR_CXX20 bool test()
{
  {
    int i = 0;
    std::reference_wrapper<int> r1 = std::ref(i);
    std::reference_wrapper<int> r2 = std::ref(r1);
    assert(&r2.get() == &i);
  }
  {
    adl::A a;
    std::reference_wrapper<adl::A> a1 = std::ref(a);
    std::reference_wrapper<adl::A> a2 = std::ref(a1);
    assert(&a2.get() == &a);
  }
  return true;
}

int main(int, char**)
{
  test();
#if TEST_STD_VER > 17
  static_assert(test());
#endif

  {
    unary_counting_predicate<bool(*)(int), int> cp(is5);
    assert(!cp(6));
    assert(cp.count() == 1);
    assert(call_pred(cp));
    assert(cp.count() == 1);
    assert(call_pred(std::ref(cp)));
    assert(cp.count() == 2);
  }

  return 0;
}