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    Endp

    Recognizer for empty lists

    In the ACL2 logic, (endp x) is the same as (atom x). See atom.

    Unlike atom, the guard for endp requires that x is a cons pair or is nil. Thus, endp is typically used as a termination test for functions that recur on a true-listp argument. See guard for general information about guards.

    Endp is a Common Lisp function. See any Common Lisp documentation for more information.

    Function: endp

    (defun endp (x)
      (declare (xargs :guard (or (consp x) (eq x nil))))
      (atom x))