;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-beginner-reader.ss" "lang")((modname circles) (read-case-sensitive #t) (teachpacks ((lib "testing.ss" "teachpack" "htdp") (lib "guess.ss" "teachpack" "htdp") (lib "master.ss" "teachpack" "htdp") (lib "draw.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "testing.ss" "teachpack" "htdp") (lib "guess.ss" "teachpack" "htdp") (lib "master.ss" "teachpack" "htdp") (lib "draw.ss" "teachpack" "htdp")))))
;; concentric-circles: posn, number, number, color, color -> boolean
;; The function draws a series of concentric circles of 
;; alternatining colors (color1, color2) with the center
;; given by the parameter center, the largest radius given by 
;; radius (>= 0), the smallest radius given by min-radius, the
;; outer color given by color1. The radius of the next circle is
;; 20 pixels less than of the current one
(define (concentric-circles center radius min-radius color1 color2)
  (cond
    [(< radius min-radius) true]
    [else (and (draw-solid-disk center radius color1)
               (concentric-circles center (- radius 20) min-radius color2 color1))]
   )
)

(start 400 400)

(concentric-circles (make-posn 200 200) 200 20 'red 'blue)