Re: Convert some Latex expressions in Emacs.

[Hongyi Zhao]

On Wed, May 18, 2022 at 7:45 AM Michael Heerdegen
<michael_heerdegen@web.de> wrote:
>
> Hongyi Zhao <hongyi.zhao@gmail.com> writes:
>
> > I rechecked the description here [1], and still can't find any
> > difference. Why do you say they are different?
> >
> > [1] https://www.emacswiki.org/emacs/peg.el
>
> PEGs can match more "complicated" things than regexps can,
> e.g. mathematical formulas.  Theory here:
>
>  https://en.wikipedia.org/wiki/Parsing_expression_grammar
>
> Unlike regexps, a PEG contains a set of named "rules" (as know from
> formal grammars).  These are allowed to be recursive and interdependent.
> This also allows to describe a "matcher" in a more structured and
> better (human)readable way.
>
> peg.el is implemented in Elisp and has some additional features like
> executing Elisp code while matching is performed.
>
> Still, when familiar with regexps, PEGs also look familiar, as you have
> already noticed.
>
> But I mentioned this only because I noticed your academical background,
> and thought that somebody who likes GAP also might be interested in that
> approach.  If you just want to get things done, DON'T look at PEGs, use
> regexps (`query-replace-regexp', C-M-%) for now.
>
> Should not be hard to do: removing stuff works by replacing with the
> empty string.  You may want to know how to refer to the matched string
> and how to use Lisp expressions to calculate parts of the replacement
> string, that's explained here:
>
>   (info "(emacs) Regexp Replace")
>
> and the rest should be doable quite trivially.  Or do you have any
> concrete questions or problems?  Or should we spell some things out?

Got the idea and the specific practices, thank you for your comments.

>
> Michael.

Best,
Hongyi