;; A Posn is a structure: Number Number ;; (define posn (x y) --- this definition already exists in DrScheme ;; An Auto is a structure: String Number Number (define-struct auto (model tank-size mpg)) ;; Examples: defining data using the constructors (define p1 (make-posn 10 20)) (define p2 (make-posn 30 20)) (define auto1 (make-auto "Ford" 15 20)) (define auto2 (make-auto "VW" 12 15)) ;; Retrieving fields of structures using the selectors: (equal? 10 (posn-x p1)) (= 20 (posn-y p2)) (equal? "Ford" (auto-model auto1)) ;(= "VW" (auto-model auto2)) Note: = compares only numbers (= 15 (auto-tank-size auto1)) (= 15 (auto-mpg auto2))