elisp regexp, what does this mean?

elisp regexp, what does this mean?

[heinz.eriksson]

I am trying to understand what the following:

(defun erl-ie-eval-expression (node)
  (interactive (list (erl-ie-read-nodename)))
  (erl-ie-read-nodename)
  (let ((end (point))
	(beg (save-excursion
	       (loop do (re-search-backward "\\(\\`\\|^\\<\\)")
		     while (looking-at "end"))
	       (point))))
    (erl-ie-evaluate beg end node t)))

Or rather the inner part involving the (scattered toothpick style)
regexp.

It is a function in distel-ie.el in http://code.google.com/p/distel/

I understand that the intent of the function is to grab a piece of
erlang source code and  pass it over for evaluation on the erlang
side. Doing so by starting from point and looking backward until...
yes, what/how?

BR

Re: elisp regexp, what does this mean?

[Lennart Borgman]

On Tue, Mar 3, 2009 at 9:22 AM,  <heinz.eriksson@gmail.com> wrote:
> I am trying to understand what the following:
>
> (defun erl-ie-eval-expression (node)
>  (interactive (list (erl-ie-read-nodename)))
>  (erl-ie-read-nodename)
>  (let ((end (point))
>        (beg (save-excursion
>               (loop do (re-search-backward "\\(\\`\\|^\\<\\)")
>                     while (looking-at "end"))
>               (point))))
>    (erl-ie-evaluate beg end node t)))
>
> Or rather the inner part involving the (scattered toothpick style)
> regexp.
>
> It is a function in distel-ie.el in http://code.google.com/p/distel/
>
> I understand that the intent of the function is to grab a piece of
> erlang source code and  pass it over for evaluation on the erlang
> side. Doing so by starting from point and looking backward until...
> yes, what/how?


(beginning of buffer) OR (beginning of line FOLLOWED BY start of word)

See (info "(elisp) Regexp Backslash")

Re: elisp regexp, what does this mean?

[Alan Mackenzie]

heinz.eriksson@gmail.com wrote:
> I am trying to understand what the following:

> (defun erl-ie-eval-expression (node)
>  (interactive (list (erl-ie-read-nodename)))
>  (erl-ie-read-nodename)
>  (let ((end (point))
>        (beg (save-excursion
>               (loop do (re-search-backward "\\(\\`\\|^\\<\\)")
>                     while (looking-at "end"))
>               (point))))
>    (erl-ie-evaluate beg end node t)))

> Or rather the inner part involving the (scattered toothpick style)
> regexp.

OK, for a start, double backslashes are really just single ones - you
need to write them double because they're in a lisp string.  If you
write it out with this substitution, and on two lines, it looks like
this:

    \(  \|   \)
      \`  ^\<

This regexp matches EITHER a match for \` OR a match for ^\<.
\` matches anything at the beginning of the (visible part of the) buffer.
^\< matches the beginning of a word at the start of a line.

This is all documented on the page "Syntax of Regexps" in the Elisp
manual.

> BR

-- 
Alan Mackenzie (Nuremberg, Germany).