argh

(define (roll_list x)
    (define (turn x)
        (cond ((null? x) x)
        (else (append (cdr x) (list (car x)))))
    )
    (define (roll x y)
        (cond ((null? y) '())
        (else (append (list x) (roll (turn x) (cdr y)))))
    )
    (roll x x )
)