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Re: Why does using aset sometimes output raw bytes?
From: |
Stephen Berman |
Subject: |
Re: Why does using aset sometimes output raw bytes? |
Date: |
Sun, 09 Dec 2018 18:32:26 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
On Sun, 09 Dec 2018 19:12:32 +0200 Eli Zaretskii <eliz@gnu.org> wrote:
>> From: Stephen Berman <stephen.berman@gmx.net>
>> Cc: help-gnu-emacs@gnu.org
>> Date: Sun, 09 Dec 2018 16:46:01 +0100
>>
>> > s0 and s2 originally include only pure ASCII characters, so they are
>> > unibyte strings. Try making them multibyte before using aset.
>>
>> Thanks, that works. But why are raw bytes inserted only with some
>> multibyte strings (e.g. with "äöüß" but not with "ſðđŋ")?
>
> Because ſ doesn't fit in a single byte, so when you insert it, the
> entire string is made multibyte, and then the other characters are
> inserted into a multibyte string.
This seems to imply that ä, ö, ü and ß do fit in a single byte? Yet
(multibyte-string-p "äöüß") returns t. So I still don't understand.
>> Also, is there some way to ensure a string is handled as multibyte
>> if it's not known what characters it contains? E.g., s0 in my
>> example sexp could be bound to some string by a function call and
>> before applying the function it is not known if the string is
>> multibyte;
>
> You should generally keep away of such situations, but you don't tell
> enough about what you are trying to accomplish to give more practical
> advice.
Nothing serious, just some experimenting.
> To answer your question: you can test whether a string is multibyte
> with multibyte-string-p, and you can make it multibyte if not. The
> only problematic situation is when a unibyte string includes non-ASCII
> bytes; what is TRT in that situation depends on the situation.
>
>> is there some way in Lisp to say "treat the value of s0 as multibyte
>> (regardless of what characters it contains)"?
>
> Not that I know of, no. And I don't really understand how could such
> a thing exist: how do you "treat as multibyte" an arbitrary byte that
> is beyond 127 decimal?
Actually, for the code I was experimenting with, it seems to suffice to
use (make-string len 128) as the input to aset (before, I had used
(make-string len 32), which led to raw bytes being displayed).
>
>> Also "aous" is also pure ASCII, so why don't raw bytes get inserted with
>> (insert (aset "aous" i (aref "äöüß" i)))?
>
> This inserts characters one by one into the current buffer, and the
> buffer is multibyte, so Emacs does the conversion. IOW, you don't
> insert the string, you insert individual characters which aset
> returns.
Ah, this makes sense. Thanks.
Steve Berman
- Why does using aset sometimes output raw bytes?, Stephen Berman, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Eli Zaretskii, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Stephen Berman, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Stephen Berman, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Eli Zaretskii, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?,
Stephen Berman <=
- Re: Why does using aset sometimes output raw bytes?, Eli Zaretskii, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Stephen Berman, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Eli Zaretskii, 2018/12/09
Re: Why does using aset sometimes output raw bytes?, Stefan Monnier, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Stephen Berman, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Stefan Monnier, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Eli Zaretskii, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Stefan Monnier, 2018/12/09
- Re: Why does using aset sometimes output raw bytes?, Eli Zaretskii, 2018/12/10
- Re: Why does using aset sometimes output raw bytes?, Stefan Monnier, 2018/12/10