Queue implementation in scheme using 2 stacks.

queue.rkt

(define first car)
(define second cadr)
(define rest cdr)
(define (third list) (car (cddr list)))
(define fourth cadddr)



(define (push v st)
 (cons v st))

(define(pop st)
 (cdr st))


(define( inStackOutStack ist ost)
 (list ist ost))

; insert into in stack
(define (enqueue v q)
  (list (push v (first q)) (second q))
  )

; dispatch and pop from outstack
(define (dequeue q)  
  (let*
(
 (disp (dispatch q))
(ins (first disp))
(outs (second disp))
 )
;expression
    (list ins (pop outs))
    )
  )

; if out stack is empty -> reverse in stack and put it in out stack --> empty in stack
(define (dispatch q)
  (let*
(
(ins (first q))
(outs (second q))
 )
    (cond
      ((null? outs) (list '() (reverse ins)))
      (#t q)
      )
    ))