I.6 Semester I Review 6

What does it do?

Write check-expects.

1. The double-circle-img function (abbeviate dci):

   (define (double-circle-image img)
     (image-width 
       (beside (circle 40 "solid" "blue)
               img
               (circle 40 "solid" "blue))))

2. Write and test a function r2d that returns a random two digit number. There is a 40% chance of the number beginning with a 2 and a 60% chance of it beginning with a 1. The ones digit should be random.

3. Gas gauge. You are making a text based gas gauge function.

   gas-gauge: number -> string

   • The readout result will be 16 X’s when the tank is full, and then should O’s for the part that is empty. For example, half full is "XXXXXXXXOOOOOOOO".
   • The gas tank can hold a maximum of 12 gallons.
   • When the tank is over half full, round the result, so 96% reads full.
   • When the tank is less than half full, always round down to avoid suddenly running out of gas. (So 6% reads empty.)

4. Graphing. You are making an animation where a red circle follows the people-coordinate graph of the function

   y = 1/600 * (x-200) * (x+200)

   • Graphing window is 500x300.
   • Both x and y axes are visible.
   • People-coordinate origin is (250,150) in computer coordinates.
   • Positive y-axis for the graph is up.
   • As you move the mouse, the red point shows on the graph is directly above/below your mouse.