;;;; This example illustrates the use of the design recipe for
;;;; functions consuming compound (structured) data.

;; (Step 1) Structure and data definition
(define-struct student (name id age major))
;; A Student is (make-student String Number Number Symbol)

;; (Step 1 continued) Student examples
(define bill (make-student "Bill" 1234 20 'math))
(define alice (make-student "Alice" 9999 25 'comp-sci))

;; (Step 2) Contract/purpose/header
;; minor? : Student -> Boolean
;; determines whether a student is under 21 years old
;; (define (minor? a-student) ...)

#| (Step 4) Template
(define (minor? a-student)
  ... (student-name a-student) ...
  ... (student-id a-student) ...
  ... (student-age a-student) ...
  ... (student-major a-student) ... )
|#

;; (Step 5) Body
(define (minor? a-student)
  (< (student-age a-student) 21))

;; (Step 3) Examples and (Step 6) Tests
(boolean=? (minor? bill) true)
(boolean=? (minor? alice) false)