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Slides

This class will be held in the location of our labs, MI 302.

Handouts

• Slides - print version

Homework

Submit your solutions to the following exercises electronically in a file called ex.scm contained in a folder called class05.

1. Go back and read the last slide from Class 4 (DISPLAY version) that we didn't get to during lecture.
   Then rewrite the following two functions using lambda:

   (define (foo x)
     (* x 12))
   
   (define (bar x)
     (let ((temp (sqrt x)))
       (* temp (+ temp 3))))
   

2. Write a function print-sum that takes a list of numbers and prints the numbers with plus signs between.
   For example:

   > (print-sum '(1 2 3))
   1 + 2 + 3
   > (print-sum '(5))
   5
   

   The function should return void.
3. Using a let closure, a returned lambda, and repeated set! calls, create a function factory make-summer that returns a procedure which takes a single number, adds it to a running sum, and returns that running sum. For example:

   > (define summer (make-summer))
   > (summer 4)
   4
   > (summer 10)
   14
   > (summer 10)
   24
   

   Hint: start with the code for make-counter in the slides.
4. (OPTIONAL) Create a function factory make-better-summer that works like make-summer, except that the returned procedure displays the entire sum at each step, and returns void.
   For example:

   > (define bs (make-better-summer))
   > (bs 10)
   10 = 10
   > (bs 4)
   4 + 10 = 14
   > (bs 8)
   8 + 4 + 10 = 22
   > (bs 16)
   16 + 8 + 4 + 10 = 38