Re: Including tex commands in a list

[tomas]

On Fri, Jan 29, 2021 at 10:52:39PM +0100, steve-humphreys@gmx.com wrote:
> I wantt to make the equivalent to the following, but still find
> difficulty doing it.
> 
> (,(concat "\\\\\\<\\(alpha\\|beta\\|gamma\\)\\>")

There's something missing up there. I'll try with just

  "\\\\\\<\\(alpha\\|beta\\|gamma\\)\\>"

The first four backslashes translate to one escaped backslash:

  (rx "\\" ...)

(two backslashes, because of Lisp string literal syntax)

Now comes a word start ("word-start" or "bow"; I'll go with the
more readable "word-start"):

  (rx "\\" word-start ...)

Next is a group, followed by a word-end:

  (rx "\\" word-start (group ...) word-end)

Within the group, there is an alternative:

  (rx "\\"
    word-start
      (group
        (or ...))
    word-end)

Now the alternative's content:
   
  (rx "\\"
    word-start
      (group
        (or "alpha" "beta" "gamma"))
    word-end)

You can check that by evaluating it in a Emacs Lisp buffer (e.g.
this *scratch* buffer Emacs comes up at start): put point after
the whole expression and hit C-x e. You get:

  "\\\\\\<\\(\\(?:\\(?:alph\\|bet\\|gamm\\)a\\)\\)\\>"

There are some spurious non-capturing groups (?: ...), and it
even factored out the trailing -a from "alpha"... etc., but
should be equivalent.

Does it help?

Cheers
 - t

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