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Re: documentation of integers, fixnums and bignums

From: Stefan Monnier
Subject: Re: documentation of integers, fixnums and bignums
Date: Sat, 08 Sep 2018 18:03:37 -0400
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux)

>>> encode-char could potentially return a value that cannot be
>>> represented as a fixnum.
>> Can this still happen?  When?
> When INDEX_TO_CODE_POINT returns a code point greater than
> most-positive-fixnum, which can happen (in theory, at least) on 32-bit
> platforms.

Can it, really?

> Formerly, such a code point caused Emacs to return a negative
> fixnum or junk, depending on the code point.

I get the impression that this possibility might have existed back in
Emacs-20 but has disappeared since.

AFAIK any Unicode codepoint fits in 22 (or even 21?) bits, and while we
may use a few extra codepoints IIUC in some corner cases, it should all
fit comfortably within our 28 bits of FIXNATs.


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