(define queue-length (lambda (queue) (vector-ref queue 0))) (define set-queue-length! (lambda (queue new-length) (vector-set! queue 0 new-length))) (define queue-start (lambda (queue) (vector-ref queue 1))) (define set-queue-start! (lambda (queue new-start) (vector-set! queue 1 new-start))) (define queue-cells (lambda (queue) (vector-ref queue 2))) (define set-queue-cells! (lambda (queue new-cells) (vector-set! queue 2 new-cells)))