Re: Emacs 23 character code space

[Eli Zaretskii]

> From: Kenichi Handa <address@hidden>
> CC: address@hidden
> Date: Wed, 05 Nov 2008 21:27:54 +0900
> 
> Attached is the remaining part.  Please reflect that to the
> document.

Thanks.  I have a few questions about this:

      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?

    @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?

      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?

TIA