various bugs

[gpeterhoff]

Hello Matt,
to_chars for std::bfloat16_t is not available

You define BOOST_CHARCONV_HAS_BRAINFLOAT16 in config.hpp, but check for BOOST_CHARCONV_HAS_BFLOAT16 in to_chars.hpp (and for BOOST_CHARCONV_HAS_BRAINFLOAT16 in from_chars.hpp).
Why these error-prone redundancies?

to_chars for FP-Types not work

./Test -nan
gets always -nan(ind)

./Test 3.3
gets

__float128:
std	3.300000	3.300000
boost	3.3000	3.3000

long double:
std	3.300000	3.300000
boost	3.3000	3.3000

double:
std	3.300000	3.300000
boost	3.300000e+00	3.300000e+00

float:
std	3.300000	3.300000
boost	3.300000e+00	3.300000e+00

_Float128:
std	3.300000	3.300000
boost	3.3000	3.3000

_Float64:
std	3.300000	3.300000
boost	3.300000e+00	3.300000e+00

_Float32:
std	3.300000	3.300000
boost	3.300000e+00	3.300000e+00

_Float16:
std	3.300781	3.300781
boost	3.300781e+00	3.300781e+00

std::bfloat16_t:
std	3.296875	3.296875
boost	3.296875e+00	3.296875e+00

Also, to_chars_result.ptr does not always match the actual written values (buffer overflow, hence the double output in print), e.g. compiled with fmt=general:

__float128:
std	3.3	3.3
boost	3.3	3.3

long double:
std	3.3	3.3
boost	3.3
	3.3


double:
std	3.3	3.3
boost	3.3e+00	3.3e+000

float:
std	3.3	3.3
boost	3.3e+00	3.3e+000

_Float128:
std	3.3	3.3
boost	3.3	3.3

_Float64:
std	3.3	3.3
boost	3.3e+00	3.3e+000

_Float32:
std	3.3	3.3
boost	3.3e+00	3.3e+000

_Float16:
std	3.30078	3.30078
boost	3.300781e+00	3.300781e+00

std::bfloat16_t:
std	3.29688	3.29688
boost	3.296875e+00	3.296875e+00

code

namespace test
{
using buffer_type = std::array<char, 1024>;

inline constexpr boost::charconv::chars_format	to_format(const std::chars_format format)	noexcept
{
	switch (format)
	{
		case std::chars_format::scientific:	return boost::charconv::chars_format::scientific;
		case std::chars_format::fixed:		return boost::charconv::chars_format::fixed;
		case std::chars_format::hex:		return boost::charconv::chars_format::hex;
		default:				return boost::charconv::chars_format::general;
	}
}

template <typename Type>
Type get_as(const int argc, const char*const*const args)	noexcept
{
	Type result{};
	if (argc > 1)	[[likely]]
	{
		const std::string_view view(args[1]);
		std::from_chars(view.data(), view.data()+view.size(), result);
	}
	return result;
}

template <typename Type>
inline std::string nameof()
{
	return boost::core::demangle(typeid(Type).name());
}

template <typename Result>
void print(const Result& res, const buffer_type& buf)
{
	if constexpr (std::is_same_v<Result, std::to_chars_result>)	std::cout << "std\t";
	else								std::cout << "boost\t";

	if (res.ec == std::errc{})	[[likely]]	std::cout << std::string_view(buf.data(), res.ptr) << '\t' << buf.data() << std::endl;
	else						std::cout << "error\n";
}

template <std::floating_point Type>
void test_to_chars(const Type value, const std::chars_format format, const int precision)
{
	buffer_type buffer{};
	std::cout << nameof<Type>() << ":\n";
	const auto rs = std::to_chars(buffer.data(), buffer.data()+buffer.size(), value, format, precision);
	print(rs, buffer);
	buffer.fill(char{});
	const auto rb = boost::charconv::to_chars(buffer.data(), buffer.data()+buffer.size(), value, to_format(format), precision);
	print(rb, buffer);
	std::cout << std::endl;
}

}	//	test

int main(const int argc, const char*const*const args)
{
	using namespace test;
	constexpr std::chars_format fmt{std::chars_format::fixed};
	constexpr int pre{6};

	test_to_chars(get_as<boost::float128_t>(argc, args), fmt, pre);
	test_to_chars(get_as<boost::float80_t>(argc, args), fmt, pre);
	test_to_chars(get_as<boost::float64_t>(argc, args), fmt, pre);
	test_to_chars(get_as<boost::float32_t>(argc, args), fmt, pre);

	test_to_chars(get_as<std::float128_t>(argc, args), fmt, pre);
	test_to_chars(get_as<std::float64_t>(argc, args), fmt, pre);
	test_to_chars(get_as<std::float32_t>(argc, args), fmt, pre);
	test_to_chars(get_as<std::float16_t>(argc, args), fmt, pre);
	test_to_chars(get_as<std::bfloat16_t>(argc, args), fmt, pre);

	return EXIT_SUCCESS;
}

thx
Gero

[mborland]

Hello Matt, to_chars for std::bfloat16_t is not available

You define BOOST_CHARCONV_HAS_BRAINFLOAT16 in config.hpp, but check for BOOST_CHARCONV_HAS_BFLOAT16 in to_chars.hpp (and for BOOST_CHARCONV_HAS_BRAINFLOAT16 in from_chars.hpp). Why these error-prone redundancies?

Fixed consistency. I had messed up FLOAT16 and BFLOAT16 once so I changed the name entirely to make it more distinguishable.

to_chars for FP-Types not work

./Test -nan gets always -nan(ind)

This is the expected value per the docs. Clang 16+ and MSVC return this value, but since I assume you're running GCC 13 +to use <stdfloat> for these test it will not.

./Test 3.3 gets

Fixed.

PR will be published shortly once the other is merged.

[gpeterhoff]

./Test -nan gets always -nan(ind)

This is the expected value per the docs. Clang 16+ and MSVC return this value, but since I assume you're running GCC 13 +to use for these test it will not.

??? Is this perhaps an MSVC "specialty"? Both intel and clang give -nan; godbolt unfortunately has no executor for MSVC so I can't check.
https://godbolt.org/z/r7fMf9bzj