; split
(define (split xs)
(let loop ((ts xs) (hs xs) (zs (list)))
(if (or (null? hs) (null? (cdr hs)))
(values (reverse zs) ts)
(loop (cdr ts) (cddr hs) (cons (car ts) zs)))))
(define (display-split xs)
(call-with-values
(lambda () (split xs))
(lambda (front back)
(display front) (newline)
(display back) (newline))))
(display-split '()) (newline)
(display-split '(1)) (newline)
(display-split '(1 2)) (newline)
(display-split '(1 2 3)) (newline)
(display-split '(1 2 3 4)) (newline)
(display-split '(1 2 3 4 5)) (newline)