play with new features added in cpp23. tested in VS2022 Version 17.8.2.

cpp23_support.cpp

#include <iostream>
#include <version>

#ifdef __cpp_lib_print
#	include <print>
#endif

#ifdef __cpp_lib_expected
#	include <expected>
#	include <system_error>
#endif

#if 0
#	if _HAS_CXX23
#		error too modern
#	endif
#endif

int main()
{
	std::cout << "supports print? " <<
#ifdef __cpp_lib_print
		"yes"
#else
		"no"
#endif
		<< "\n";

	std::cout << "supports expected? " <<
#ifdef __cpp_lib_expected
		"yes"
#else
		"no"
#endif
		<< "\n";

#ifdef __cpp_lib_print
	std::cout << "\n";
	std::println("hello {}", 6 * 7);
#endif

#ifdef __cpp_lib_expected
	std::cout << "\n";
	{
		std::expected<int, std::errc> result1;
		std::println("[1] has_value: {}", result1.has_value());
	}
	{
		std::expected<int, std::errc> result2(std::unexpect_t{}, std::errc::invalid_argument);
		std::println("[2] has_value: {}", result2.has_value());
		std::println("    errc: {}", std::underlying_type_t<std::errc>(result2.error()));
	}
	{
		std::expected<int, std::errc> result3(std::in_place_t{}, 6);
		auto derived_result = result3.transform(
			[](int x)
			{
				return x * 7;
			});
		std::println("[3] {}", derived_result.value());
		std::println("    {}", *derived_result);
	}
#endif

	return 0;
}

// https://www.youtube.com/watch?v=Dk_C_E8AtRs&t=934s
//     => https://devblogs.microsoft.com/cppblog/cpp23s-optional-and-expected/
//         => https://bartoszmilewski.com/2014/10/28/category-theory-for-programmers-the-preface/

output.txt

supports print? yes
supports expected? yes

hello 42

[1] has_value: true
[2] has_value: false
    errc: 22
[3] 42
    42