#lang plait
(define MEMORY (make-vector 100 -1))
(define next-addr 0)
(define (reset) (set! next-addr 0))
(define (write-and-bump v)
  (let ([n next-addr])
    (begin
      (vector-set! MEMORY n v)
      (set! next-addr (add1 next-addr))
      n)))

(define (store-num n)
  (write-and-bump n))
(define (read-num a)
  (vector-ref MEMORY a))

(test (read-num (store-num 42)) 42)