;; The first three lines of this file were inserted by DrScheme. 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 review2) (read-case-sensitive #t) (teachpacks ((lib "draw.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "draw.ss" "teachpack" "htdp") (lib "gui.ss" "teachpack" "htdp")))))
;; Write a contract and a purpose for this function

(define (f list1 list2)
  (cond
    [(and (empty? list1) (empty? list2)) empty]
    [(or (empty? list1) (empty? list2)) (error 'f "The lists must be of equal length")]
    [else (cons (first list1) (cons (first list2) (f (rest list1) (rest list2))))]
  )
)

;; what value will this produce?
(f (list 1 2 3) (list 4 5 6))

(define (g list1 list2)
  (cond
    [(and (empty? list1) (empty? list2)) empty]
    [(or (empty? list1) (empty? list2)) (error 'g "The lists must be of equal length")] 
    [else (append (g (rest list1) (rest list2)) (list (first list2) (first list1)))]
   )
)

;; what value will this produce?
(g (list 1 2 3) (list 4 5 6))


(define-struct mypair (left right))

;; Write a function that, given a list of mypairs of numbers, creates a list of 
;; sums of left and right

(define lop (list (make-mypair 2 3) (make-mypair 5 6) (make-mypair 3 7)))

;(sum-pair lop)
;; expected
(list 5 11 10)

;; write a function that counts the total number of elements of nested lists
;; of arbitrary nesting

;(number-elements (list 1 2 (list 4 5) (list 3 (list 6))))
;; expected value
6

;; Exercise 14.1.4 -- self-referential structures
;; http://www.htdp.org/2003-09-26/Book/curriculum-Z-H-19.html#node_sec_14.1
;; http://cda.morris.umn.edu/~elenam/1301_fall09/examples/recursive_structures.ss

;; write a function add-bst that adds a node to a binary search tree according 
;; to the ordering
;; Exercise 14.2.5 
;; http://www.htdp.org/2003-09-26/Book/curriculum-Z-H-19.html#node_sec_14.2
;; http://cda.morris.umn.edu/~elenam/1301_fall09/examples/bst.ss