bug#10494: 24.0.92; Syntax table and non-ASCII character interaction

[Eli Zaretskii <eliz@gnu.org>]

> From: npostavs@users.sourceforge.net
> Cc: 10494@debbugs.gnu.org,  aaronecay@gmail.com
> Date: Sat, 13 Aug 2016 14:14:49 -0400
> 
> > Sorry, I guess I was thinking of \cl.  It will not match ’, although
> > it might be expected.
> 
> Which could be fixed by (modify-category-entry ?’ ?l).

This is Emacs, right?

But the fact that you can do this doesn't yet mean you should want to,
or that we should encourage it.

> I would suggest this additional docstring patch, because I was confused
> at first as to what CATEGORY was supposed to be (I looked around a bit
> for how to create some kind of "category object"):
> 
> diff --git i/src/category.c w/src/category.c
> index 4397f66..31ac2ec 100644
> --- i/src/category.c
> +++ w/src/category.c
> @@ -336,6 +336,7 @@ DEFUN ("modify-category-entry", Fmodify_category_entry,
>  the current buffer's category table.
>  CHARACTER can be either a single character or a cons representing the
>  lower and upper ends of an inclusive character range to modify.
> +CATEGORY must be a category name (a character between ` ' and `~').
>  If optional fourth argument RESET is non-nil,
>  then delete CATEGORY from the category set instead of adding it.  */)
>    (Lisp_Object character, Lisp_Object category, Lisp_Object table, Lisp_Object reset)

How about mentioning describe-categories as well?

> > Anyway, my point is that these char-tables should really be treated as
> > read-only by Lisp applications.
> 
> Right, but I think this bug is about the user modifying stuff.

Which is even less recommendable, IMO.  How many users really
understand the implications?