2.48.rkt

#lang racket/gui
(require graphics/graphics)
(open-graphics)
(define vp (open-viewport "A Picture Language" 500 500))

(define draw (draw-viewport vp))
(define (clear) ((clear-viewport vp)))
(define line (draw-line vp))

(define (make-vect x y)
  (cons x y))

(define (xcor-vect v)
  (car v))

(define (ycor-vect v)
  (cdr v))

(define (add-vect v1 v2)
  (make-vect (+ (xcor-vect v1) (xcor-vect v2)) (+ (ycor-vect v1) (ycor-vect v2))))

(define (sub-vect v1 v2)
  (make-vect (- (xcor-vect v1) (xcor-vect v2)) (- (ycor-vect v1) (ycor-vect v2))))

(define (scale-vect s v)
  (make-vect (* s (xcor-vect v)) (* s (ycor-vect v))))

(define (make-segment v1 v2)
  (cons v1 v2))

(define (start-segment s)
  (car s))

(define (end-segment s)
  (cdr s))