Re: prettify-symbols-mode to handle "\alpha-\beta" ...

[pietru@caramail.com]

> Sent: Saturday, February 06, 2021 at 11:04 AM
> From: "Gregory Heytings" <gregory@heytings.org>
> To: pietru@caramail.com
> Cc: emacs-devel@gnu.org
> Subject: Re: prettify-symbols-mode to handle "\alpha-\beta" ...
>
> 
> >>>> (defun texinfo-prettify-symbols-compose-p (start end _match)
> >>>>    ;; We know the matches all start with a backslash and end with
> >>>>    ;; a word-element.
> >>>>    (not (or (memq (char-before start) '(?\\))
> >>>>             (memq (char-syntax (or (char-after end) ?\s)) '(?w))
> >>>>             (nth 8 (syntax-ppss)))))
> >>>> (add-hook 'texinfo-mode-hook
> >>>>            (lambda ()
> >>>>              (push '("\\alpha" . ?α) prettify-symbols-alist)
> >>>>              (push '("\\beta" . ?β) prettify-symbols-alist)
> >>>>              (setq prettify-symbols-compose-predicate 'texinfo-prettify-symbols-compose-p)
> >>>>              (prettify-symbols-mode)))
> >>>
> >>> That is not completely correct because for "\alpha-\beta", only \beta 
> >>> is prettified.
> >>
> >> No, \alpha-\beta is prettified correctly.  Tested with Emacs 25, 26, 27 
> >> and 28.
> >
> > Have tried it in a texinfo document using
> >
> > @tex
> > $\alpha -\beta \gamma \alpha - \beta \gamma \alpha, \alpha. \alpha- \alpha() \alpha[]$
> > @end tex
> >
> 
> This works correctly with vanilla Emacs, with the "defun" and "add-hook" 
> above.

So I have to add the following defun in prog-mode.el?

 (defun texinfo-prettify-symbols-compose-p (start end _match)