forward-sexp confusion

Question

The following code is an excerpt from the elisp tutorial, section 14.6.

(while (re-search-forward "^(defun" nil t)
    (setq lengths-list (cons (count-words-in-defun) lengths-list)))

Placing the cursor just before the code and executing (forward-sexp) will fail, because of the ( symbol imbedded in the regexp "^(defun". My ugly remedy is below:

(setq my-regexp (concat "^" (char-to-string 40) "defun"))
(while (re-search-forward my-regexp nil t)
    (setq lengths-list (cons (count-words-in-defun) lengths-list)))

Is there a less ugly approach? Alternatively, is there a wrapper for (forward-sexp) that provides optional arguments to ignore imbedded quotes and ignore imbedded comments (e.g. ;...)?

If not, I will reference this posting as a feature request for both forward-sexp and backward-sexp.

Answer 1

While forward-sexp works just fine for me on the code in question (in Emacs 27.0.50), the standard workaround is to add a single backslash, e.g., "^\(defun ".

One place where it actually is needed is when doc string contains code. Emacs uses a simple heuristic ("line starting with a paren starts a function") for beginning-of-defun and code like this:

(defun foo (...)
  "Blah blah...
Sample code:
(foo 1 2 3)
Blah"
  (actual code))

breaks the heuristic.

The standard workaround is to add a backslash:

(defun foo (...)
  "Blah blah...
Sample code:
\(foo 1 2 3)
Blah"
  (actual code))