;; The first three lines of this file were inserted by DrRacket. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-intermediate-lambda-reader.ss" "lang")((modname |lists of structs|) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
;; Helene Martin, Garfield high school
;; 10/6/2010
;; Lists and lists of structs review

;; A list-of-number is
;; - empty, or
;; - (cons number list-of-number)

;; Template over a list-of-number
;;(define (lon-template alon)
;;  (cond [(empty? alon) ...]
;;        [(cons? alon) ... (first alon) 
;;                      ... (lon-template (rest alon)) ... ]))
(define LIST1 (cons 2 (cons 4 (cons 1 (cons 3 empty)))))
(define LIST2 (cons 6 (cons 5 (cons 4 (cons 8 (cons 3 empty))))))

;; sort: list-of-number -> list-of-number
(define (sort-it a-lon)
  (cond [(empty? a-lon) empty]
        [else (insert (first a-lon) (sort-it (rest a-lon)))]))

;; insert: number list-of-number -> list-of-number
;; inserts an element into a sorted list, preserving sorted order
(define (insert num a-lon)
  (cond [(empty? a-lon) (cons num empty)]
        [else (cond [(<= num (first a-lon)) (cons num a-lon)]
                    [else (cons (first a-lon) 
                                (insert num (rest a-lon)))])]))

(check-expect (insert 2 empty) (cons 2 empty))
(check-expect (insert 2 (cons 3 empty)) (cons 2 (cons 3 empty)))
(check-expect (insert 2 (cons 1 (cons 3 empty))) (cons 1 (cons 2 (cons 3 empty))))

;; A student is (make-student string number)
;; Student ids start with the graduation year (11xxx for those who will graduate in '11)
(define-struct student (name id))

(define ADAM (make-student "Adam" 11123))
(define MICHAEL (make-student "Michael" 13123))
(define QUYNH (make-student "Quynh" 11234))
(define LANE (make-student "Lane" 13234))

(define STUDENTS (cons ADAM (cons MICHAEL (cons QUYNH (cons LANE empty)))))

;; Template over a student
;;(define (student-template a-student)
;;  ... (student-name a-student) ...
;;  ... (student-id a-student) ...)

;; A list-of-student
;; - empty, or
;; - (cons student list-of-student)

;; Template over a list of students
;;(define (los-template a-los)
;;  (cond [(empty? a-los) ...]
;;        [(cons? a-los) ... (student-template (first a-los)) 
;;                      ... (lon-template (rest a-los)) ... ]))

;; senior?: student -> boolean
(define (senior? a-student)
  (and (>= (student-id a-student) 11000) 
       (< 1200 (student-id a-student) 12000)))

(check-expect (senior? QUYNH) true)
(check-expect (senior? MICHAEL) false)

;; extract-seniors: list-of-student -> list-of-student
(define (extract-seniors a-los)
  (cond [(empty? a-los) empty]
        [else (cond [(senior? (first a-los)) (cons (first a-los) (extract-seniors (rest a-los)))]
                    [else (extract-seniors (rest a-los))])]))

(check-expect (extract-seniors STUDENTS) (cons ADAM (cons QUYNH empty)))