ANSI Common Lisp 6 Iteration 6.1 The LOOP Facility 6.1.4 Termination Test Clauses
18.104.22.168 Examples of WHILE and UNTIL clauses
(loop while (hungry-p) do (eat))
;; UNTIL NOT is equivalent to WHILE.
(loop until (not (hungry-p)) do (eat))
;; Collect the length and the items of STACK.
(let ((stack '(a b c d e f)))
(loop for item = (length stack) then (pop stack)
(6 A B C D E F)
;; Use WHILE to terminate a loop that otherwise wouldn't terminate.
;; Note that WHILE occurs after the WHEN.
(loop for i fixnum from 3
when (oddp i) collect i
while (< i 5))