(format stream "`~C'" char))
(t (format stream "<~(~:C~)>" char))))
+(defun skip-until (scanner token-types &key keep-end)
+ "This is the implementation of the `skip-until' parser."
+ (do ((consumedp nil t))
+ ((member (token-type scanner) token-types)
+ (unless keep-end (scanner-step scanner))
+ (values nil t (or keep-end consumedp)))
+ (when (scanner-at-eof-p scanner)
+ (return (values token-types nil consumedp)))
+ (scanner-step scanner)))
+
+(defun parse-error-recover (scanner parser recover)
+ "This is the implementation of the `error' parser."
+ (multiple-value-bind (result win consumedp) (funcall parser)
+ (cond ((or win (and (not consumedp) (scanner-at-eof-p scanner)))
+ ;; If we succeeded then there's nothing for us to do here. On the
+ ;; other hand, if we failed, didn't consume any tokens, and we're
+ ;; at end-of-file, then there's not much hope of making onward
+ ;; progress, so in this case we propagate the failure rather than
+ ;; trying to recover. And we assume that the continuation will
+ ;; somehow arrange to report the problem, and avoid inundating the
+ ;; user with error reports.
+ (values result win consumedp))
+ (t
+ ;; Now we have to do some kind of sensible error recovery. The
+ ;; important thing to do here is to make sure that we make some
+ ;; progress. If we consumed any tokens then we're fine, and we'll
+ ;; just try the provided recovery strategy. Otherwise, if we're
+ ;; not at EOF, then we can ensure progress by discarding the
+ ;; current token. Finally, if we are at EOF then our best bet is
+ ;; simply to propagate the current failure back to the caller, but
+ ;; we handled that case above.
+ (syntax-error scanner result :continuep t)
+ (unless consumedp (scanner-step scanner))
+ (funcall recover)))))
+
;;;--------------------------------------------------------------------------
;;; Token scanning.
~mdw / sod / blobdiff