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differentiate cons & list

2 posts · 6325 views

dericbytes

#1 Fri Dec 07, 2012 6:53 pm

I want to know when an item is a cons and when it is a list

(consp (cons 1 1))

> t

(listp (cons 1 1))

(consp (list 1 1))

(listp (list 1 1))

(nth 1 (cons 1 1))

> error not a list

Goheeca

#2 Sat Dec 08, 2012 11:15 am

Re: differentiate cons & list

What about this:

(defun true-list-p (list)
  (cond ((null list) t)
        ((consp list) (true-list-p (cdr list)))
        (t nil)))

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