Programming Languages

Before we tackle lists, we'll get used to simply building and and manipulating structured data. Remember to follow the Design Recipe for structures.

1. Provide a datatype definition for a structure called a pit, representing points in time since midnight. A point in time consists of three numbers: hours, minutes, and seconds.
   
   Now develop the function time-diff. It consumes two pits, t1 and t2, and returns the number of seconds from t1 to t2. 
   
   For example:
   (time-diff (make-pit 1 2 3) (make-pit 4 5 6)) 
   
   should yield 10983. If you would like, I have written up a complete solution, which may give you a sense for what I think a full solution looks like.
   
   
2. Provide a structure definition and a data definition for a game-score. A game-score is characterized by two pieces of information: a symbol representing the name of the team and a number representing the points-scored by that team.
   
   
3. Develop a function that consumes two game-scores from a particular game and returns the name of the team that won or 'tie if the scores were equal. 
   


4. Develop a datatype definition for a position in two-dimensional space called a posn. A posn should have an x and a y coordinate. 
   
   
5. Provide a datatype definition for shapes. There are three kinds of shapes:
   1. A circle has a center (center isa posn?) and a radius (radius isa number?)
   2. A square has an upper-left corner (corner isa posn?) and a length (length isa number?)
   3. A rectangle has an upper-left corner (corner isa posn?), width (width isa number?), and height (height isa number?) 

   In each case, remember to provide a clear comment regarding the structure along with its definition.

6. Develop the function area that consumes a shape and computes its area.
   
   
7. Develop the function in-shape? that consumes a shape and a posn, and returns true if that posn is within the shape, false otherwise.

For each of these functions, I would like you to follow the design recipe and have small tests written before you write the functions themselves. You should write tests that you are confident exercise all of your code.

For example, if I was writing the function

(define (add a b) (+ a b))

then I would write, before writing the function:

;; CONTRACT
;; add : number number -> number
(= (add 3 5) 8)
(= (add 0 0) 0)

and so on. You should have already encountered the design recipe in your reading of HtDP. I'll mention it at the start of lab again.