(define make-rectangle cons)
(define rectangle-height car)
(define rectangle-width cdr)

(define make-isosceles-triangle cons)
(define isosceles-triangle-side car)
(define isosceles-triangle-base cdr)

(define isosceles-triangle-perimeter
  (lambda (r)
    (+ (* (isosceles-triangle-side r) 2) (isosceles-triangle-base r))))

;; We didn't finish writing this in class
;(define isosceles-triangle-area
;  (lambda (r)
;    (* .5 (* (isosceles-triangle-base r) (sqrt (- (expt (isosceles-triangle-base r)
;                                                    2)
;                                                 (expt 

(define right-triangle-perimeter
  (lambda (r)
    (+ (right-triangle-base r) (right-triangle-height r)
       (sqrt (+ (expt (right-triangle-height r) 2) (expt (right-triangle-base r) 2))))))

(define make-right-triangle cons)
(define right-triangle-height cdr)
(define right-triangle-base car)

(define rectangle-area
  (lambda (r)
    (* (rectangle-height r)
       (rectangle-width r))))

(define rectangle-perimeter
  (lambda (r)
    (* 2 (+ (rectangle-height r)
            (rectangle-width r)))))

(define tagged-datum 
  (lambda (type value)
    (cons type value)))

(define type car)

(define contents cdr)

(define list-of-shapes
  (list (tagged-datum 'rectangle (make-rectangle 4 10))
        (tagged-datum 'isosceles-triangle (make-isosceles-triangle 6 2))
        (tagged-datum 'isosceles-triangle (make-isosceles-triangle 5 8))
        (tagged-datum 'right-triangle (make-right-triangle 3 4))))

(define perimeter
  (lambda (td)
    (cond ((equal? (type td) 'rectangle)
           (rectangle-perimeter (contents td)))
          ((equal? (type td) 'isosceles-triangle)
           (isosceles-triangle-perimeter (contents td)))
          ((equal? (type td) 'right-triangle)
           (right-triangle-perimeter (contents td)))
          (else
           (error "I have no clue how to find the perimeter of a" (type td))))))