Since lazymicro doesn't have a display function that can be called while
in lazymicro, we have to resort to the following trickery to demonstrate
that evaluation really is lazy.  Th following definitions can be typed
into lazymicro when it is expecting keyboard input.

(define yes 0)
(define no 0)
(define (change-yes) (set! yes 'yes))
(define (change-no) (set! no 'no))
(define (my-if test t f)
  (cond (test t)
        (else f)))

Now if you execute

(my-if #t (change-yes) (change-no))

only yes changes.  Similarly, if you execute

(my-if #f (change-yes) (change-no))

only no changes.