-(defun gnus-score-regexp-bad-p (regexp)
- "Test whether REGEXP is safe for Gnus scoring.
-A regexp is unsafe if it matches newline or a buffer boundary.
-
-If the regexp is good, return nil. If the regexp is bad, return a
-cons cell (SYM . STRING), where the symbol SYM is `new' or `bad'.
-In the `new' case, the string is a safe replacement for REGEXP.
-In the `bad' case, the string is a unsafe subexpression of REGEXP,
-and we do not have a simple replacement to suggest.
-
-See Info node `(gnus)Scoring Tips' for examples of good regular expressions."
- (let (case-fold-search)
- (and
- ;; First, try a relatively fast necessary condition.
- ;; Notice ranges (like [^:] or [\t-\r]), \s>, \Sw, \W, \', \`:
- (string-match "\n\\|\\\\[SsW`']\\|\\[\\^\\|[\0-\n]-" regexp)
- ;; Now break the regexp into tokens, and check each:
- (let ((tail regexp) ; remaining regexp to check
- tok ; current token
- bad ; nil, or bad subexpression
- new ; nil, or replacement regexp so far
- end) ; length of current token
- (while (and (not bad)
- (string-match
- "\\`\\(\\\\[sS]?.\\|\\[\\^?]?[^]]*]\\|[^\\]\\)"
- tail))
- (setq end (match-end 0)
- tok (substring tail 0 end)
- tail (substring tail end))
- (if;; Is token `bad' (matching newline or buffer ends)?
- (or (member tok '("\n" "\\W" "\\`" "\\'"))
- ;; This next handles "[...]", "\\s.", and "\\S.":
- (and (> end 2) (string-match tok "\n")))
- (let ((newtok
- ;; Try to suggest a replacement for tok ...
- (cond ((string-equal tok "\\`") "^") ; or "\\(^\\)"
- ((string-equal tok "\\'") "$") ; or "\\($\\)"
- ((string-match "\\[\\^" tok) ; very common
- (concat (substring tok 0 -1) "\n]")))))
- (if newtok
- (setq new
- (concat
- (or new
- ;; good prefix so far:
- (substring regexp 0 (- (+ (length tail) end))))
- newtok))
- ;; No replacement idea, so give up:
- (setq bad tok)))
- ;; tok is good, may need to extend new
- (and new (setq new (concat new tok)))))
- ;; Now return a value:
- (cond
- (bad (cons 'bad bad))
- (new (cons 'new new))
- (t nil))))))
-