Reference no: EM13186260

Question 1

An accumulator is a procedure that is called repeatedly with a single numeric argument and accumulates its arguments into a sum. Each time it is called, it returns the currently accumulated sum. Write a procedure make-accumulator that generates accumulators, each maintaining an independent sum. The input to make-accumulator will correctly specify the initial value of the sum; for example

(define A (make-accumulator 5))
(A 10)
15
(A 10)
25

Question 2

Write a procedure (make-queue) that produces independent first-in-first-out queue objects, using a message-passing style.

For example:

(define queue1 (make-queue))
(define queue2 (make-queue))

Write procedures to manipulate queues. At a minimum [0.5 marks each]:
1. (queue1 'empty?): boolean
2. (queue1 'enqueue! item): adds item to the queue
3. (queue1 'front): returns the next element of the queue that would be removed on dequeue
4. (queue1 'back): returns the last element of the queue that would be removed on dequeue (i.e. the most recent element added)
5. (queue1 'dequeue!): throws away the front element
6. (queue1 'print): prints some representation of the queue from front to back