;; --- CSU213 Fall 2006 Lecture Notes ---------
;; Copyright 2006 Viera K. Proulx

;; Lecture 6: September 18, 2006
;; Designing Methods for Unions of Classes
;; HtDP version - data definitions, examples, purpose statements and contracts

;; An IShape is one of
;; -- (make-circle Posn Number String)
;; -- (make-square Posn Number String)

(define-struct circle (center radius color))
(define-struct square (nw size color))

;; Examples:

(define pt1 (make-posn 0 0))
(define pt2 (make-posn 3 4))
(define pt3 (make-posn 7 1))

(define c1 (make-circle (make-posn 50 50) 10 "red"))
(define c2 (make-circle (make-posn 50 50) 30 "red"))
(define c3 (make-circle (make-posn 30 100) 30 "blue"))

(define s1 (make-square (make-posn 50 50) 30 "red"))
(define s2 (make-square (make-posn 50 50) 50 "red"))
(define s3 (make-square (make-posn 20 40) 10 "green"))

;; Function purpose statements and contracts --- with default bodies

;; to compute the area of this shape
(define (area this-shape) 0)

;; to compute the distance form this shape to the origin
(define (distTo0 this-shape) 0)

;; to increase the size of this shape by the given increment
(define (grow this-shape x) this-shape)

;; is the area of this shape is bigger than the area of the that shape?
(define (biggerThan? this-shape that-shape) true)

;; does this shape (including the boundary) contain the given point?
(define (contains? this-shape pt) true)