13. Intro Exercises 0

Objectives:

• I can simplify Boolean expressions.
• I know the two key simplifications of boolean=?.

1. Simplify each as much as possible.

   1. (< 30 50)
   2. (string=? "move" "button-down")
   3. (<= 30 40 60 50)
   4. (image? 100)
   5. (string-ci<? "cat" "DOG")
   6. (and (>= 50 40) (string<=? "wet" "frog"))
   7. (not (string=? "button-down" "drag"))

2. Assume each variable mentioned below has the correct type to be used in the comparisons. Simplify as much as possible.

   1. (and (string=? word "apple") (string=? word "banana"))
   2. (and (<= x 100) (>= x 30) (not (= x 120)))

3. What is wrong with the following code? Briefly explain how to fix it.

   1. (= x (or 5 10 15))
   2. (boolean=? wet? "true")

4. What’s wrong with the following code? How would you fix it?

    (define (bad-apple? fruit)
        (string=? "rotten apple"))
   

5. This code is not wrong to Racket, but a human will not like it. Why not?

    (define name? "Micah")
   

6. Make a “truth table” with columns cold? (not cold?) and (boolean=? cold? true). Can you see a simpler way to write the boolean=? column?

7. Make a “truth table” with columns cold? (not cold?) and (boolean=? cold? false). Can you see a simpler way to write the boolean=? column?

8. Quick, edit this code so it has better programming style. I found four edits.

    (define (bad-day raining clothes)
        (and (string=? "wet" (substring clothes 0 3)) raining))
   

9. Simplify as much as possible.

   1. (boolean=? legs-hurt? false)
   2. (or (boolean=? cross-fit? true) (and (< 0 miles-ran) (>= miles-ran 2.0)))

10. The function home-early? takes in a booleans baby-dolphin-day?, family-pickup?, and fast-bus?. You get home early if you get picked up by your family or if it is a baby dolphin day and you ride a fast bus. Write this function.