Custom Query (1030 matches)

Use case:

(setf *print-circle* t)
(format nil "~{~A ~:*~A, ~}" '("77" "88"))
=> "#1=77 #1#, #2=88 #2#, "

Expected value

=> "77 77, 88 88, "

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.

(defun f () (setf (symbol-function 'f) (lambda () 1)) (f))

Such a function will cause an infinite loop when it is call at first time but when interupting and calling (f) again, it has been modified to (lambda () 1) I have tried several CL implementation and they all behave correctly, they return 1 and do not cause an infinite loop.