Re: [review][JSON] json::value as a vocabulary type

From: Zach Laine (whatwasthataddress_at_[hidden])
Date: 2020-09-25 13:09:12

On Fri, Sep 25, 2020 at 6:11 AM Mathias Gaunard via Boost
<boost_at_[hidden]> wrote:
>
> On Thu, 24 Sep 2020 at 10:57, Andrzej Krzemienski via Boost
> <boost_at_[hidden]> wrote:
>
> > My understanding of a "vocabulary type" is that it should be usable (not
> > necessarily with maximum efficiency) for *any* usage. In the case of JSON
> > that would mean that I should be able to represent any value that
> > corresponds to a valid JSON when converted to text. I do not think that
> > json::value can claim that without the ability to serialize arbitrarily big
> > numbers.
>
> I fully agree with this statement.
> json::value *needs* to support arbitrary numbers. It's incomplete without it.
> Maybe the author of multiprecision can advise on the best type to use
> there (gmp or mpfr?).

This is not a reasonable requirement.  std::string is the canonical
C++ vocabulary type.  On 32-bit systems, it cannot represent 5GB-long
strings.  Depending on platform limitations, it usually cannot even
represent more than 2GB-long strings.  Computers are limited to finite
resources.  Putting finite limits on the representation of all kinds
of values is normal, not unexpected -- this is especially true of
numeric values.

Zach