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Re: Emacs 23 character code space
From: |
Kenichi Handa |
Subject: |
Re: Emacs 23 character code space |
Date: |
Wed, 26 Nov 2008 10:41:01 +0900 |
User-agent: |
SEMI/1.14.3 (Ushinoya) FLIM/1.14.2 (Yagi-Nishiguchi) APEL/10.2 Emacs/23.0.60 (i686-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) |
In article <address@hidden>, Eli Zaretskii <address@hidden> writes:
> A character set is a set of characters, and it assigns a unique code
> point to each character belonging to the set. Emacs decodes a
> specific code point of a specific character set to an Emacs character.
> Does this mean a character set is equivalent to a coding-system,
> meaning that a coding-system is a mapping between a character set and
> the Emacs internal codepoints?
No. A coding-system is a mapping between a sequence of
characters and a sequence of bytes. The byte sequence
contains a byte not mapped to a character. For instance,
iso-2022 uses escape sequence, UTF-16 uses surrogate pairs.
> @defun charset-dimension charset
> This function returns the dimension of @var{charset}. Here, dimension
> means the number of bytes required to represent the highest code point
> (not an Emacs character code) of a character. For example, the
> dimension of @code{iso-8859-1} is one, the dimension of
> @code{japanese-jisx0208} is two, and the dimension of @code{unicode}
> is three.
> @end defun
> I decided not to document this. I think the concept of charset
> dimension is too obscure to explain, and not really needed for Lisp
> programs, unless they need to define a new charset, or display a
> charset, and those are already done by Emacs infrastructure. Do you
> see any problems with not documenting this function?
I think no.
> A translation table has two extra slots. The first is either
> @code{nil} or a translation table that performs the reverse
> translation; the second is the maximum number of characters to look up
> for translation.
> Could you please elaborate on the second extra slot: when and for what
> purpose would there be a need to look up characters for translation?
To enable sequence-to-char translation. See the description
of make-translation-table-from-alist.
---
Kenichi Handa
address@hidden
- Emacs 23 character code space, Eli Zaretskii, 2008/11/01
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/01
- Re: Emacs 23 character code space, Kenichi Handa, 2008/11/02
- Re: Emacs 23 character code space, Kenichi Handa, 2008/11/03
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/03
- Re: Emacs 23 character code space, Kenichi Handa, 2008/11/04
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/04
- Re: Emacs 23 character code space, Kenichi Handa, 2008/11/05
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/05
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/22
- Re: Emacs 23 character code space,
Kenichi Handa <=
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/25
- Re: Emacs 23 character code space, Kenichi Handa, 2008/11/25
- Re: Emacs 23 character code space, Kenichi Handa, 2008/11/25
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/26
- Re: Emacs 23 character code space, Juanma Barranquero, 2008/11/26
- Re: Emacs 23 character code space, Stephen J. Turnbull, 2008/11/26
- Re: Emacs 23 character code space, Kenichi Handa, 2008/11/26
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/26
- Re: Emacs 23 character code space, Kenichi Handa, 2008/11/26
- Re: Emacs 23 character code space, Eli Zaretskii, 2008/11/29