While

Repetitive structure with continuation condition

    (while logical_expression
        do_statements
    )

Examples

(setq test 1)
(while (<= test 4) (princ test) (princ "\n") (setq test (+ 1 test)) )

(defun test_while (start end)
    (setq test start)
    (while (<= test end)
        (test_cond test)
        (setq test (+ 1 test))
    )
)

(test_while 0 4)
(test_while 1 1)
(test_while 0 -1)