#lang plait
(require (typed-in racket/base
                   [char->integer : (Char -> Number)]
                   [integer->char : (Number -> Char)]
                   [number->string : (Number -> String)]
                   [vector->list : ((Vectorof Number) -> (Listof Number))])
         (typed-in racket/vector
                   [vector-copy : ((Vectorof Number) Number Number -> (Vectorof Number))]))

(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))

(define (store-str s)
  (let ([a0 (write-and-bump (string-length s))])
    (begin
      (map write-and-bump
           (map char->integer (string->list s)))
      a0)))

(define (read-str a)
  (let* ([len (vector-ref MEMORY a)]
         [start (+ a 1)]
         [end (+ start len)]
         [slice (vector-copy MEMORY start end)]
         [lst (vector->list slice)])
    (list->string (map integer->char lst))))

(test (read-str (store-str "cookie monster"))
      "cookie monster")