From: Kenichi Handa <handa@m17n.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: emacs-devel@gnu.org
Subject: Re: Emacs 23 character code space
Date: Wed, 26 Nov 2008 10:41:01 +0900 [thread overview]
Message-ID: <E1L59On-0005aa-BP@etlken.m17n.org> (raw)
In-Reply-To: <uiqqfipn3.fsf@gnu.org> (message from Eli Zaretskii on Sat, 22 Nov 2008 20:25:52 +0200)
In article <uiqqfipn3.fsf@gnu.org>, Eli Zaretskii <eliz@gnu.org> 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
handa@ni.aist.go.jp
next prev parent reply other threads:[~2008-11-26 1:41 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-01 14:20 Emacs 23 character code space Eli Zaretskii
2008-11-01 16:46 ` Eli Zaretskii
2008-11-03 1:34 ` Kenichi Handa
2008-11-03 12:45 ` Kenichi Handa
2008-11-03 20:13 ` Eli Zaretskii
2008-11-04 7:35 ` Kenichi Handa
2008-11-04 20:19 ` Eli Zaretskii
2008-11-05 12:27 ` Kenichi Handa
2008-11-05 18:23 ` Eli Zaretskii
2008-11-22 18:25 ` Eli Zaretskii
2008-11-26 1:41 ` Kenichi Handa [this message]
2008-11-26 4:13 ` Eli Zaretskii
2008-11-26 4:24 ` Kenichi Handa
2008-11-26 4:58 ` Kenichi Handa
2008-11-26 20:26 ` Eli Zaretskii
2008-11-26 22:52 ` Juanma Barranquero
2008-11-27 1:10 ` Stephen J. Turnbull
2008-11-27 1:35 ` Kenichi Handa
2008-11-26 20:18 ` Eli Zaretskii
2008-11-27 1:29 ` Kenichi Handa
2008-11-29 17:12 ` Eli Zaretskii
2008-12-02 5:40 ` Kenichi Handa
2008-11-28 13:19 ` Eli Zaretskii
2008-12-02 5:44 ` Kenichi Handa
2008-12-02 19:40 ` Eli Zaretskii
2008-11-29 12:01 ` Eli Zaretskii
2008-11-22 16:28 ` Eli Zaretskii
2008-11-23 4:16 ` Stefan Monnier
2008-11-23 11:22 ` Eli Zaretskii
2008-11-26 1:51 ` Kenichi Handa
2008-11-23 8:29 ` Ulrich Mueller
2008-11-23 11:11 ` Eli Zaretskii
2008-11-23 11:55 ` Ulrich Mueller
2008-11-24 3:06 ` Stefan Monnier
2008-11-26 1:31 ` Kenichi Handa
2008-11-22 17:03 ` New function: what-file-line, used when writing gdb script richardeng
2008-11-07 7:21 ` Emacs 23 character code space Kenichi Handa
2008-11-07 10:27 ` Eli Zaretskii
2008-11-07 11:52 ` Kenichi Handa
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