Quiz 7 Answers, CS 257

As an adolescent I aspired to lasting fame, I craved factual certainty, and I thirsted for a meaningful vision of human life - so I became a scientist. This is like becoming an archbishop so you can meet girls.

- Matt Cartmill

1. Fill in the table (2 points each)
   

   what you type	what Scheme prints
   `((+ 1 2) ,(+ 1 2) 4)	((+ 1 2) 3 4)
   (cons '(a b) '(c (d) e))	((a b) c (d) e)
   (append '((a b) (c d)) '(e f))	((a b) (c d) e f)
   (car ''a)	quote
   (if 1 2 3)	2

2. Define rev-noah, a function that takes two lists with an equal number of elements, packs them up two-by-two, and returns them in reverse order:

   (rev-noah '(a b c) (d e f))      ; ((c f) (b e) (a d))
   (rev-noah '() '())               ; ()
   

   Your definition should work (7 points) and be tail recursive (3 points).

   ---

   (define (rev-noah lis1 lis2)
     (aux lis1 lis2 '()))
   
   (define (aux lis1 lis2 res)
     (if (null? lis1)
         res
         (aux (cdr lis1) (cdr lis2) `((,(car lis1) ,(car lis2)) ,@rev))))