Re: syntax parsing of non-contiguous regions

[Andreas Politz <politza@fh-trier.de>]

Emacs offers the possibility of setting the character-syntax on the fly.

(info "(elisp) Setting Syntax Properties")

Out of boredom, I actually tried to implement something like this.

(defun foo-mode ()
  (interactive)
  (kill-all-local-variables)
  (set-syntax-table
   (let ((tb (make-syntax-table)))
     (modify-syntax-entry ?{ ". 1" tb)
     (modify-syntax-entry ?% ". 23" tb)
     (modify-syntax-entry ?} ". 4" tb)
     tb))

  (setq font-lock-defaults
        '(nil nil nil nil nil
              (font-lock-syntactic-keywords
               .
               ((foo-find-other-comment
                 ; generic comment syntax prohibits regular comments
                 ; inside it
                 (1 "!")                
                 (2 "!")))))))

(defun foo-find-other-comment (limit)
  "Starting at point, find the next occurence of '!' not inside a
string or comment."
  (let (success)
    (while (and (not success)
                (re-search-forward
                 "\\(!\\).*\\(\n?\\)" limit t))
      (setq success (let ((st (syntax-ppss (match-beginning 0))))
                      (not (or (nth 4 st)     ;comment
                               (nth 5 st))))) ;string
      (unless (eobp)
        (forward-char))
      (when success
        (goto-char (match-end 0))))
    success))



-ap