I.9 Semester I Review 9

Basics

1. There will be a white Christmas if the temperature is below 32 and there is water?

    ;; white-christmas?: boolean(water?) number(temperature)
    ;;                   -> boolean
    (define (white-christmas? water? temperature)
        ...)
   

2. Give examples showing how to get “ACE”, “BETA”, and “CROW”.

    (define (q2 x y? z)
        (cond [(and y? (< x 30))         "ACE"]
              [(or (not y?)
                   (string=? z "good"))  "BETA"]
              [else                      "CROW"]))
   

3. Write this function:

    ;; q3 : number number number string -> number
    (define (q3 m x y e)
        ...)
   

   • give -10 when x > 200 and e is “button-down”
   • give -20 when x < 200 and e is “button-down”
   • give m otherwise

Simple Animation

• The model is a number, a multiple of 10 from 10 through 90.
• Losing is indicated by adding 100 to the number, so the losing models will be 110, 120, …, 190.
• Winning is indicated by adding 1000 to the number, so the winning models will be 1010, 1020, …, 1090.

Examples: when the model is 40, you see “PLAY 40”; when the model is 130, you see “LOSE 30”; when the model is 1070, you see “WIN 70”.

5. Write the win? : model(number) -> boolean function to give true when the model indicates a win. Write a similar function lose?. Write two check-expects for your lose? function, picking a winning value and a “playing” value check-expect for your win? function
6. Make a draw handler that shows WIN, LOSE, or PLAY above the number. Make sure you can still see the number in all cases.
7. Make a key handler that randomly choses 10 through 90.
8. Clicking the mouse on the right side of the screen wins (button-down and x>50). Clicking the mouse on the left side loses. No other mouse actions (including move) change the model.
9. Test your code in a big-bang.
10. Write should-stop? that will stop when the model indicates a win or a lose. Add it into your big bang. Use your ordinary draw handler as the final scene draw handler.

Notes

Some people did confusing things.

• temperature should not end in a question mark because it is not a true or false value
• You know water? is a true or false, not a string, because its name ends in a question mark.
• Do not compare (string=? water? "water"), see the previous.
• Boolean variables are themselves true or false; they do not need to be compared using boolean=?. The variable name poses a question, and the value inside answers it.
• The win? function should not just be the opposite of the lose? function.