Re: Boost.Charconv review runs January 15th - 25th, 2024

From: Peter Dimov (pdimov_at_[hidden])
Date: 2024-01-31 15:59:58

Dominique Devienne wrote:
> On Wed, Jan 31, 2024 at 1:38 PM Peter Dimov via Boost
> <boost_at_[hidden] <mailto:boost_at_[hidden]> > wrote:
> 
> 
> 	Viktor Sehr wrote:
> 	> I think boost::charconv should add one convenience function as
> follows:
> 	> // Returns std::nullopt on error
> 	> template <typename NumberType>
> 	> std::optional<NumberType> boost::charconv::to_number(const
> 	> std::string_view& sv) noexcept;
> 
> 	This throws away the error code
> 
> 
> 
> But sometimes that's all you want. That's kinda the point from Viktor I guess.

It's actually never what you want the way from_chars is specified, because
0.000[more 0...]001 fails with ERANGE, whereas 1.000[same 0...]001 succeeds
and returns 1.0.

I don't really know of a use case where this is what one wants.

> Not that an `expected` or `outcome` return type is bad; but it is more complex.

It's not any more complex for the user; the interface is the same as optional's
if you don't need the error.

Returning `optional` is almost always a design mistake.