HW 4.1

Due: before class on Monday 17 November

Consider the following Scheme program:

(define x 10)

(define f
  (lambda (x)
    (display (+ x 20))
    (newline)))

(f 3)
(f 4)

(define g
  (lambda (a)
    (lambda ()
      (set! a (* a 2))
      (f a))))

((g 5))

(define h (g 3))
(h)
(h)

Run the code in https://try.scheme.org/

What is the output from running this code?
Draw the frames and closures created from running this code, like we saw in class 4.2

(Hint: use a separate piece of paper. You should end up with 11 frames and 4 closures in total.)
Write equivalent Python code that does exactly the same thing.
Write a Scheme function (make-account) to simulate a bank account.

It should return another function (a lambda) which accepts a command (either 'deposit or 'withdraw) and an amount, updates the balance accordingly, and returns the new balance.

Here is an example showing how it should work:
```
> (define rich (make-account))
> (rich 'deposit 1000000)
1000000
> (define poor (make-account))
> (poor 'deposit 10)
10
> (poor 'withdraw 100)
-90
> (rich 'deposit 100)
1000100
```