Debugging Grammars

Tip 1

Guruguru doesn’t have a grammar debugger yet. The following function is useful when debugging a grammar by hand; use this in an action and it prints the rule and the yield (the text that was parsed.)

(defun gg-debug ()
  (message "%s: %s"
           rule
           (buffer-substring-no-properties gg-start gg-end)))

Tip 2

M-x regexp-builder is useful for writing regular expressions.

Tip 3

Emacs’ default stack limit is low. Non-trivial grammars typically exceed this limit. You can set a higher limit, for example:

(setq max-lisp-eval-depth 15000)
(setq max-specpdl-size 45000)