optional/test/optional_test_cmp_none.cpp

// Copyright (C) 2014 Andrzej Krzemienski.
// Copyright (C) 2024 Alexander Grund
//
// Use, modification, and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// See http://www.boost.org/lib/optional for documentation.
//
// You are welcome to contact the author at:
//  akrzemi1@gmail.com

#include "boost/optional/optional.hpp"

#ifdef BOOST_BORLANDC
#pragma hdrstop
#endif

#include "boost/core/lightweight_test.hpp"
#include "boost/none.hpp"


struct SemiRegular // no operator==
{ 
private: void operator==(SemiRegular const&) const {}
private: void operator!=(SemiRegular const&) const {}
};

void test_equal_to_none_of_noncomparable_T()
{
  boost::optional<SemiRegular> i = SemiRegular();
  boost::optional<SemiRegular> o;
  
  BOOST_TEST(i != boost::none);
  BOOST_TEST(boost::none != i);
  BOOST_TEST(o == boost::none);
  BOOST_TEST(boost::none == o);
}

void test_comparison_to_none()
{
    using boost::none;
    boost::optional<SemiRegular> i = SemiRegular();
    // the default ordering of optional<size_t> is{ boost::none, 0, 1, 2, ... }
    // Hence boost::none < i for any engaged i
    // and all others operators ( ==, !=, <, <=, >, >= ) follow

    BOOST_TEST(!(i == none));
    BOOST_TEST(i != none);
    BOOST_TEST(!(i < none));
    BOOST_TEST(!(i <= none));
    BOOST_TEST(i > none);
    BOOST_TEST(i >= none);
    // Comparison is symmetric
    BOOST_TEST(!(none == i));
    BOOST_TEST(none != i);
    BOOST_TEST(none < i);
    BOOST_TEST(none <= i);
    BOOST_TEST(!(none > i));
    BOOST_TEST(!(none >= i));

    // An un-engaged optional is always equal to none
    boost::optional<SemiRegular> o;
    BOOST_TEST(o == none);
    BOOST_TEST(!(o != none));
    BOOST_TEST(!(o < none));
    BOOST_TEST(o <= none);
    BOOST_TEST(!(o > none));
    BOOST_TEST(o >= none);
    // Comparison is symmetric
    BOOST_TEST(none == o);
    BOOST_TEST(!(none != o));
    BOOST_TEST(!(none < o));
    BOOST_TEST(none <= o);
    BOOST_TEST(!(none > o));
    BOOST_TEST(none >= o);
}

int main()
{
  test_equal_to_none_of_noncomparable_T();
  return boost::report_errors();
}