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True-listp

Recognizer for proper (nil-terminated) lists

True-listp is the function that checks whether its argument is a list that ends in, or equals, nil.

For a discussion of whether requiring lists to be nil-terminated is right for you, see std::strict-list-recognizers.

Function: true-listp

(defun true-listp (x)
  (declare (xargs :guard t))
  (if (consp x)
      (true-listp (cdr x))
    (eq x nil)))

True-list-listp: Recognizer for true (proper) lists of true lists
List-fix: (list-fix x) converts x into a true-listp by, if necessary, changing its final-cdr to nil.
True-list-fix: Coerce to a true list
The-true-list: Coerce an expected true list to a true list
Std/lists/true-listp: Lemmas about true-listp available in the std/lists library.