Custom Query (1030 matches)

The following code signals an error about the :sign keyword argument. The culprit seems to be the method on T, which prevents the method on list to run. If I omit the method on T, or I define it e.g. on built-in-class, the error is gone.

(defgeneric render (obj &rest args))

(defmethod render ((obj t) &key)
  (print obj))

(defmethod render ((obj list) &rest args)
  (mapc (lambda (item)
          (apply #'render item args))
        obj))

(defmethod render ((obj number) &key sign)
  (print (* sign obj)))

(render (list 1 2 3 4) :sign -1)

According to my reading of CLHS (7.6.4 & 7.6.5), no error should be signaled. Indeed, I have tested this with SBCL and it runs just fine.

? (make-random-state t)
> Error: Can't determine primary IP interface
> While executing: CCL::PRIMARY-IP-INTERFACE-ADDRESS, in process listener(1).
> Type :POP to abort, :R for a list of available restarts.
> Type :? for other options.

System is Windows XP SP3. CCL is version 1.4.

It should be possible for gf dispatch to run simultaneously in multiple threads without introducing inconsistencies in CLOS internals (e.g. caches).

FWIW, here's what sbcl does about this: ​http://lisp-ecoop07.bknr.net/pdf/31662.