\f
;;;; type-ish predicates
-;;; a helper function for various macros which expect clauses of a
-;;; given length, etc.
-(eval-when (:compile-toplevel :load-toplevel :execute)
- ;; Return true if X is a proper list whose length is between MIN and
- ;; MAX (inclusive).
- (defun proper-list-of-length-p (x min &optional (max min))
- ;; FIXME: This implementation will hang on circular list
- ;; structure. Since this is an error-checking utility, i.e. its
- ;; job is to deal with screwed-up input, it'd be good style to fix
- ;; it so that it can deal with circular list structure.
- (cond ((minusp max)
- nil)
- ((null x)
- (zerop min))
- ((consp x)
- (and (plusp max)
- (proper-list-of-length-p (cdr x)
- (if (plusp (1- min))
- (1- min)
- 0)
- (1- max))))
- (t nil))))
-
;;; Is X a list containing a cycle?
(defun cyclic-list-p (x)
(and (listp x)