Using std::expected in C++ #cpp #functional

using-expected.cpp

auto parse_int(std::string_view str)
	-> std::expected<int, std::domain_error>
{
	int i;
	std::stringstream ss;
	ss << str;
	ss >> i;
	if(ss.fail())
		return std::make_unexpected( std::domain_error("value is not an integer") );
	return i;
}

auto result = parse_int( input );
if( result )
	std::cout << *result << "\n";
else
	std::cerr << "Error: " << result.error().what() << "\n";