I.4 Semester I Review 4

Remember to practice writing check-expects for your functions, so you have a way to make progress.

1. Analyze the program segment below.

   (define initial "large fluffy bunny")
   (define (f model) (+ 1 (string-length model)))
   (define (g model) (text model 25 "black"))
   (define (k model x y e) (string-append model x))
   (define (p model w) (substring model 1))
   (big-bang initial ...)

   1. Is f suitable for a tick handler? Explain.
   2. What could g be used for?
   3. Are either k or p suitable handlers? If so, for what?
   4. Write a useful, correct check-expect for the function p.
   5. Write a useful, correct check-expect for the function k.

2. The median is the middle number in a list of sorted numbers. Write the function median that works for three numbers.

       median: number number number -> number

   Writing tests is the most important part of this exercise.

3. Structures

   1. Make a structure scn that has fields for a string, a color, and a number.

   2. Create an example of your structure and put it in a variable.

   3. Write a function that gets the number out of your structure and adds one to it.

      sincr: scn -> int

   4. The sdraw function draws a circle with the given color, using the number for the radius. Unless the string is square, in which case draw a square in the same way.

      sdraw: scn -> image

   5. Write a function scolor that makes a new structure with the given color, not changing any of the other fields.

      scolor: scn color(new) -> scn

   6. The scat function takes in two structures and combines them by appending the strings and adding the numbers. The color of the result will be the same as the first structure’s color.

      scat: scn scn -> scn