Quiz #2

1a)
Draw the environment diagram created by the following expressions evaluated in order. Draw everything created even if it isn't reachable at the end. Draw box and pointer diagrams to represent pairs. You may redraw atoms instead of having multiple pointers pointing to one atom.

> (define (quiz-cons a b)
     (let ((cons (cons a b)))
        (lambda (mesg)
           (define wasted 6)) ))
           (cond ((eq? 'bark mesg) b)
                 ((eq? 'woof mesg) a)
                 ((eq? 'cons mesg) cons)
                 (else (error "ERR" mesg)) )
> (define apple (quiz-cons 'apple 'core))
> (define no-apple (quiz-cons 'apple "Oh! There's more!"))
> (cdr (no-apple 'cons))
> (define ghastly (cons (apple 'bark) (no-apple 'woof)))
> (set-car! ghastly apple)

1b)
Define the selectors quiz-car and quiz-cdr so that the object created by quiz-cons mimics a pair, except for lacking mutators.

2)
Draw the concurrencty diagram for:
(Note: This is not in the book.)

(parallel-execute-and-block fn1
                            (begin fn2
                            (parallel-execute-and-block fn1 fn4))
                            fn3)

Given that fn1 and fn2 share the same serializer S1, and fn3, fn2, and fn4 share the same serializer S2.