libstdc++-v3/testsuite/20_util/function_objects/not_fn/1.cc

// Copyright (C) 2014-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3.  If not see
// <http://www.gnu.org/licenses/>.

// { dg-do run { target c++17 } }

#include <functional>
#include <testsuite_hooks.h>

using std::not_fn;

int func(int, char) { return 0; }

struct F
{
  bool operator()() { return false; }
  bool operator()() const { return true; }
  bool operator()(int) { return false; }
};

void
test01()
{
  auto f1 = not_fn(func);
  VERIFY( f1(1, '2') == true );

  auto f2 = not_fn( [] { return true; } );
  VERIFY( f2() == false );

  auto f3 = not_fn( F{} );
  VERIFY( f3() == true );
  VERIFY( f3(1) == true );
  const auto f4 = f3;
  VERIFY( f4() == false );
}

template<typename F, typename Arg>
auto foo(F f, Arg arg) -> decltype(not_fn(f)(arg)) { return not_fn(f)(arg); }

template<typename F, typename Arg>
auto foo(F f, Arg arg) -> decltype(not_fn(f)()) { return not_fn(f)(); }

struct negator
{
    bool operator()(int) const { return false; }
    void operator()() const {}
};

void
test02()
{
  foo(negator{}, 1); // PR libstdc++/66998
}

void
test03()
{
  struct X { bool b; };
  X x{ false };
  VERIFY( not_fn(&X::b)(x) );
}

void
test04()
{
  struct abstract { virtual void f() = 0; };
  struct derived : abstract { void f() { } };
  struct F { bool operator()(abstract&) { return false; } };
  F f;
  derived d;
  VERIFY( not_fn(f)(d) );
}

void
test05()
{
  auto nf = std::not_fn([] { return false; });
  auto copy(nf); // PR libstdc++/70564
}

void
test06()
{
  struct Boolean {
    Boolean operator!() noexcept(false) { return *this; }
  };
  struct F {
    Boolean operator()() { return {}; }
  };
  F f;
  auto notf = std::not_fn(f);
  using NotF = decltype(notf);
  static_assert( std::is_invocable<NotF>::value, "cannot negate" );
  static_assert( !noexcept(notf()), "conversion to bool affects noexcept" );
}

void
test07()
{
  struct NonNegatable { };
  struct F {
    NonNegatable operator()() { return {}; }
  };
  F f;
  auto notf = std::not_fn(f);
  using NotF = decltype(notf);
  static_assert( !std::is_invocable<NotF>::value, "cannot negate" );
}

int
main()
{
  test01();
  test02();
  test03();
  test04();
  test05();
  test06();
  test07();
}