;; A ListOfG:
;; --empty
;; --(cons g ListOfG)


;;examples of lists;
;;list-of-Numbers:
empty
(cons 1 empty)
(cons 1 (cons 5 (cons 10 (cons 4 empty))))

;;list-of-Symbols:
empty
(cons 'a empty)
(cons 'a (cons 'b (cons 'c empty)))

;;list-of-Strings: 
empty
(cons "one" empty)
(cons "one" (cons "two" (cons "three" empty)))

;;list-of-posns (or structures)
empty
(cons (make-posn 1 2) empty)
(cons (make-posn 1 2) (cons (make-posn 3 4) (cons (make-posn 5 6) empty)))

;; TODO: Try running these examples and see the results it produces



;; If you haven't seen it yet, there is an easier way to make lists
;; We can use the keyword, list, to make lists identical to the lists above
;; TODO: Try uncommenting the next few lines and running them, compare the results

;(list 1 5 10 4)
;(list 1)
;(list 'a 'b 'c)
;(list 'a)
;(list "one" "two" "three")
;(list "one")
;(list (make-posn 1 2) (make-posn 3 4) (make-posn 5 6))

;; Now just to make sure try comparing some of these lists using equal?

;(equal? (list 1 2 3) (cons 1 (cons 2 (cons 3 empty))))


;;  TODO: Try some more to tests 




;; Now go the Language and choose Begining Student with List Abbreviations
;; TODO:  Now try running the program again. 






;; Notice cons and empty no longer appear in the results
;; Just because the list appears different doesn't mean it is, we can still check lists using cons? and empty?

;(list)
;(list (make-posn 1 2))
;(list (make-posn 1 2) (make-posn 3 4) (make-posn 5 6))

;; Now take the three lists above and run them through this function:
;;  Sum-of-posns which takes a list of posns and creates list of numbers.
;;     Each number in the list is the sum of the x and y coordinate for each posn


;TODO: Go through the steps of building this function, ie, the contract, the template, examples, etc..






;;Contract

;;TEMPLATE

;;Examples





;; You can use this language or continue to use Begining Student
;;         You can also use (cons a-list empty) or the (list list-elements) representation with either language
;; Remember, that all list does is hide the cons and empty from you, they are still there its just not shown to you