Re: modern regexes in emacs

[Juri Linkov]

> If I read the petitioners correctly, they want a global setting that
> permits them to type a(b|c) instead of a\(b\|c\) in isearch-forward-regexp
> and all other interactive commands.

This would be really trivial to do when we'll have a function that
will convert an extended regexp string into rx form like what
the xr package does, i.e. like the function ‘xr’, a new function
‘exr’ could convert an extended regexp - as opposed to basic regexp
as noted in https://www.regular-expressions.info/gnu.html

Then similarly to ‘isearch-symbol-regexp’, the implementation will be just
4 lines:

  (isearch-define-mode-toggle extended "\\" isearch-extended-regexp "\
  Turning on extended regexp search turns off basic regexp mode.")

  (defun isearch-extended-regexp (string)
    (rx (exr string)))

that will also automatically support extended regexp interactively in
occur, query-replace-regexp...