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Re: compute ISBN-10, char-to-int?
From: |
Stefan Monnier |
Subject: |
Re: compute ISBN-10, char-to-int? |
Date: |
Sat, 07 Sep 2019 13:13:45 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
>> > [...] since chars in Emacs Lisp are simply integers, and since
>> > encoding is almost-UTF-8 which is basically ASCII [...]
>> Actually, encoding is not relevant here. We are not talking about how
>> characters are stored in buffers and strings, we are talking about the
>> characters themselves. A character is represented by an integer whose
>> value is that character's Unicode codepoint.
> Well, if it's always Unicode code point, then we can make the above
> "official".
(- c ?0) and (+ n ?0) work not just with Unicode code points, but with
code points in any character set that is sane enough to put the digits
from 0 to 9 consecutively in this order. That's the case in ASCII,
EBCDIC, and all other charsets I know.
I think the main threat could come from a charset where digits appear
multiple times (e.g. some kind of iso-2022 system where some of the
sub-charsets also include digits), in which case (+ n ?0) would still
work but (- c ?0) could occasionally fail. But, I don't know of such
a charset either.
Stefan
- compute ISBN-10, char-to-int?, Emanuel Berg, 2019/09/04
- Re: compute ISBN-10, char-to-int?, tomas, 2019/09/05
- Re: compute ISBN-10, char-to-int?, Emanuel Berg, 2019/09/05
- Re: compute ISBN-10, char-to-int?, Eli Zaretskii, 2019/09/05
- Re: compute ISBN-10, char-to-int?, tomas, 2019/09/05
- Re: compute ISBN-10, char-to-int?, Emanuel Berg, 2019/09/05
- Re: compute ISBN-10, char-to-int?, Eli Zaretskii, 2019/09/06
- Re: compute ISBN-10, char-to-int?, tomas, 2019/09/06
- Re: compute ISBN-10, char-to-int?, Emanuel Berg, 2019/09/06
- Re: compute ISBN-10, char-to-int?, Eli Zaretskii, 2019/09/06
- Re: compute ISBN-10, char-to-int?,
Stefan Monnier <=
- Re: compute ISBN-10, char-to-int?, Eli Zaretskii, 2019/09/07
- Re: compute ISBN-10, char-to-int?, Stefan Monnier, 2019/09/07
- Re: compute ISBN-10, char-to-int?, Eli Zaretskii, 2019/09/07
- Re: compute ISBN-10, char-to-int?, Stefan Monnier, 2019/09/07
- Re: compute ISBN-10, char-to-int?, Emanuel Berg, 2019/09/09
- Re: compute ISBN-10, char-to-int?, Perry Smith, 2019/09/09