1-11-4.rkt~

;; The first three lines of this file were inserted by DrRacket. 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 1-11-4) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f () #f)))
; A Polygon is one of:
; – (list Posn Posn Posn)
; – (cons Posn Polygon)

; a plain background image 
(define MT (empty-scene 50 50))
 
; Image Polygon -> Image
; renders the given polygon p into img
(define (render-poly img p)
  img)

(check-expect
  (render-poly MT triangle-p)
  (scene+line
    (scene+line
      (scene+line MT 20 10 20 20 "red")
      20 20 30 20 "red")
    30 20 20 10 "red"))


(define triangle-p
  (list
    (make-posn 20 10)
    (make-posn 20 20)
    (make-posn 30 20)))
 

(define square-p
  (list
    (make-posn 10 10)
    (make-posn 20 10)
    (make-posn 20 20)
    (make-posn 10 20)))