#lang racket
(require "hw2.rkt")
 (define prg '( (define BLUE "stroke:blue") (define GREEN "stroke:green") (define END 40) (define (start x d) (when (< x END) (if (> d 0) (line x 0 (+ x 10) 10 BLUE) (line x 10 (+ x 10) 0 GREEN) ) (start (+ x 10) (* d -1)) ) ) )) (display (execute 200 200 prg '(start 0 1)))