How to grok a complicated regex?

[Marcin Borkowski]

Hi all,

so I have this monstrosity [note: I know, there are much worse ones,
too!]:

"\\`\\(?:\\\\[([]\\|\\$+\\)?\\(.*?\\)\\(?:\\\\[])]\\|\\$+\\)?\\'"

(it's in the org-latex--script-size function in ox-latex.el, if you're
curious).

I'm not asking “what does this match” – I can read it myself.  But it
comes with a considerable effort.  Are you aware of any tools that might
help to understand such regexen?

I know about re-builder, but it’s well suited for constructing a regex
matching a given string, not the other way round.

For instance, show-paren-mode does not really help here, since it seems
to pair “\\(“ with unescaped “)”.

Any ideas?

(Note: if there are no such tools, I might be tempted to craft one.  Two
things that come to my mind are proper highlighting of matching parens
of various kinds and eldoc-like hints for all the regex constructs –
I never seem to remember what does “\\`” do, for instance.  Also,
displaying the string with single backslashes and not in the way it is
actually typed in in Elisp, with all the backslash escaping, might be
helpful.  Would there be a demand for such a tool larger than one
person?)

Best,

-- 
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University