CS 2010 Lab 2 Instructor Plan

1. Evaluate by hand:

   (define (h x)
     (* 7 x))
   (h 10)

2. Evaluate by hand:

   (define (f a)
     (* 7 (cond
   	[(= a 3) 9]
   	[(= a 4) 10])))
   (f 3)

3. Evaluate by hand:

   (define (t a)
     (* 7 (cond
   	[(= a 3) 9]
   	[(= a 4) 10]
   	[else 11])))
   (t 5)

4. Evaluate by hand:

   (define (g a b c)
     (make-posn 10 (posn-y (cond
   			 [(= c 12) a]
   			 [else b]))))
   (g (make-posn 1 2) (make-posn 3 4) 11)

5. Write the function order which takes two numbers and produces a posn containing the two numbers. The X part of the posn should contain the smaller number, and the Y part the larger.
   • (order 10 11) = (make-posn 10 11)
   • (order 7 5) = (make-posn 5 7)
6. Write the function max-part, which takes a posn and returns either the X or Y part, whichever is larger.
   • (max-part (make-posn 10 11)) = 11
   • (max-part (make-posn 7 5)) = 7

For the programs, don't bother with a lab2 handin.

We haven't yet talked about the design recipe for compound data in lecture. So you should suggest the following guideline: when they're writing a function that consumes a posn p, they should write (posn-x p) and (posn-y p) as a start for the function body.