1-5-9.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 1-5-9) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f () #f)))
; A SpaceGame is a structure:
;   (make-space-game Posn Number). 
; interpretation (make-space-game (make-posn ux uy) tx)
; describes a configuration where the UFO is 
; at (ux,uy) and the tank's x-coordinate is tx

(define-struct space-game [ufo tank])