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Add operator<< for monostate

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This commit is contained in:
Peter Dimov
2022-01-31 17:55:26 +02:00
parent 573ef77382
commit 5e2bce1baa
3 changed files with 23 additions and 6 deletions
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7
include/boost/variant2/variant.hpp
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@ -2263,6 +2263,13 @@ template<class Os, class T> struct is_output_streamable<Os, T, decltype( std::de
} // namespace detail
template<class Ch, class Tr>
std::basic_ostream<Ch, Tr>& operator<<( std::basic_ostream<Ch, Tr>& os, monostate const& )
{
os << "monostate";
return os;
}
template<class Ch, class Tr, class T1, class... T,
class E = typename std::enable_if< mp11::mp_all< detail::is_output_streamable<std::basic_ostream<Ch, Tr>, T>... >::value >::type >
std::basic_ostream<Ch, Tr>& operator<<( std::basic_ostream<Ch, Tr>& os, variant<T1, T...> const& v )

3
test/is_output_streamable.cpp
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@ -30,9 +30,12 @@ int main()
BOOST_TEST_TRAIT_FALSE((boost::variant2::detail::is_output_streamable<std::ostream, X>));
BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, Y>));
BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::monostate>));
BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::variant<int, float, std::string>>));
BOOST_TEST_TRAIT_FALSE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::variant<int, float, X>>));
BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::variant<int, float, Y>>));
BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::variant<boost::variant2::monostate, int, float>>));
return boost::report_errors();
}

19
test/variant_ostream_insert.cpp
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@ -20,17 +20,24 @@ template<class T> std::string to_string( T const& t )
int main()
{
variant<int, float, std::string> v( 1 );
{
BOOST_TEST_EQ( to_string( monostate() ), "monostate" );
}
BOOST_TEST_EQ( to_string( v ), to_string( 1 ) );
{
variant<monostate, int, float, std::string> v;
v = 3.14f;
BOOST_TEST_EQ( to_string( v ), to_string( monostate() ) );
BOOST_TEST_EQ( to_string( v ), to_string( 3.14f ) );
v = 1;
BOOST_TEST_EQ( to_string( v ), to_string( 1 ) );
v = "test";
v = 3.14f;
BOOST_TEST_EQ( to_string( v ), to_string( 3.14f ) );
BOOST_TEST_EQ( to_string( v ), to_string( "test" ) );
v = "test";
BOOST_TEST_EQ( to_string( v ), to_string( "test" ) );
}
return boost::report_errors();
}