diff options
Diffstat (limited to 'lisp/emacs-lisp/regexp-opt.el')
| -rw-r--r-- | lisp/emacs-lisp/regexp-opt.el | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/lisp/emacs-lisp/regexp-opt.el b/lisp/emacs-lisp/regexp-opt.el index 00f72e284ad..b6104f22e7d 100644 --- a/lisp/emacs-lisp/regexp-opt.el +++ b/lisp/emacs-lisp/regexp-opt.el @@ -279,7 +279,9 @@ Merges keywords to avoid backtracking in Emacs's regexp matcher." (defun regexp-opt-charset (chars) "Return a regexp to match a character in CHARS. -CHARS should be a list of characters." +CHARS should be a list of characters. +If CHARS is the empty list, the return value is a regexp that +never matches anything." ;; The basic idea is to find character ranges. Also we take care in the ;; position of character set meta characters in the character set regexp. ;; @@ -326,13 +328,15 @@ CHARS should be a list of characters." (while (>= end start) (setq charset (format "%s%c" charset start)) (setq start (1+ start))))) - ;; - ;; Make sure a caret is not first and a dash is first or last. - (if (and (string-equal charset "") (string-equal bracket "")) - (if (string-equal dash "") - "\\^" ; [^] is not a valid regexp - (concat "[" dash caret "]")) - (concat "[" bracket charset caret dash "]")))) + + ;; Make sure that ] is first, ^ is not first, - is first or last. + (let ((all (concat bracket charset caret dash))) + (pcase (length all) + (0 regexp-unmatchable) + (1 (regexp-quote all)) + (_ (if (string-equal all "^-") + "[-^]" + (concat "[" all "]"))))))) (defun regexp-opt--contains-prefix (strings) |