;; Abstraktionen für Repräsentationsabstraktion

(define make-type
  (lambda (name)
    name))

(define typed-value-maker
  (lambda (type)
    (lambda (value)
      (cons type value))))
  
(define typed-value-selector
  (lambda (type)
    (lambda (value)
      (if (equal? type (car value))
          (cdr value)
          (error "type mismatch")))))

(define typed-value-predicate
  (lambda (type)
    (lambda (value)
      (and (pair? value)
           (equal? type (car value))))))