C++ Logo


Advanced search

Re: std::max_format_size pre-proposal

From: Mateusz Janek <mateusz.janek6_at_[hidden]>
Date: Sun, 21 Mar 2021 10:12:01 +0100
Thank you for the input.

Didn't know about avoiding templates in `to/from_chars`. Like you said, in
this case it would be difficult.

Should've been more explicit. I meant using `formatted_size` with carefully
chosen value and assuming info like signed representation, e.g.
`numeric_limits<int>::min()`. Then you have the maximum size. Additionally,
like you said, the result is not `constexpr`.

I'm curious what do you and other people think about the idea in general?
Does it sound like a good addition to the library? Is it worth creating a
formal paper and going through the review process?

Best regards,
Mateusz Janek

sob., 20 mar 2021 o 14:58 Jason McKesson via Std-Proposals <
std-proposals_at_[hidden]> napisaƂ(a):

> The `to/from_chars` interface explicitly avoids the use of templates.
> Or rather, the in-specification definition of it does. There's not
> really a simple way to avoid that here without introducing a bunch of
> function names for no reason.
> I think the reasoning behind not using templates was to make it more
> acceptable for C to implement the interface. However, the `constexpr`
> nature of these APIs makes a non-macro C equivalent API impossible, so
> you may as well use template arguments.
> You note in the proposal that you could use `formatted_size`, but you
> couldn't, as even if it were `constexpr`, it is still computing the
> size of a specific value. You're interested in the maximum possible
> size.
> As to the location of these functions, they should go into the
> `charconv` header and the `format` header, since both of them consume
> these values. Sticking them in `limits` doesn't really make sense,
> since these values are about formatting more than numeric limitations
> (that's why they require additional parameters and are functions
> rather than variables). Also, it would require that `limits`
> include/export parts of `charconv`, since these APIs use
> `std::char_format`.
> --
> Std-Proposals mailing list
> Std-Proposals_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/std-proposals

Received on 2021-03-21 04:12:15