;; The first three lines of this file were inserted by DrScheme. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "reader.ss" "plai" "lang")
(require (planet schematics/schemeunit:3)
         (planet schematics/schemeunit:3/text-ui))

(define-struct elephant (legs weight))
(define-struct snake    (length weight))

;; CONTRACT
;; get-weight :: (U elephant? snake?) -> number?
;; PURPOSE
;; To tell me how much an animal weighs.
(define (get-weight animal)
  (cond
    [(elephant? animal) (elephant-weight animal)]
    [(snake? animal)    (snake-weight animal)]
    ))
  


(define geoffrey (make-elephant 4 1000))
(check-equal? 
 (get-weight geoffrey)
 1000)