;;;
;;; Recursive patterns
;;;
;;;  Write each higher order procedure and confirm
;;;  that it works similary to the built-in procedure.
;;;
;;;  Also try writing the higher order procedures:
;;;   -  find-first 
;;;   -  test-all
;;;   -  count-true
;;;

(define (every proc sent)
  "")

(define (keep pred sent)
  "")

(define (accumulate cmbr sent)
  "")

;; (find-first odd? '(2 4 1 5)) -> 1
(define (find-first pred sent)
  "")

;; (test-all odd? '(3 1 2 4)) -> #f
(define (test-all pred sent)
  "")

;; (count-true odd? '(1 1 2 3 1 4)) -> 4
(define (count-true pred sent)
  "")

;;;
;;; Zip
;;;
;;;  Write a procedure that weaves to sentences
;;;  together. 
;;;
;;;  (zip '(1 2 3) '(a b c d e))
;;;                 -> (1 a 2 b 3 c d e)
;;;
;;;  (Make it as short as you possible can)
;;;

(define (zip sent1 sent2)
  "")

;;;
;;; Reverse
;;;
;;;  Write reverse using higher order procedures.
;;;
;;;  (Make it work for words AND sentences)
;;;

(define (reverse wd-or-sent)
  "")

;;;
;;; Repeated
;;;
;;;  Write repeated, which takes in a procedure with 
;;;  one argument and a number 'n', and returns a procedure
;;;  that is executed n times.
;;;

(define (repeated proc n)
  "")


;;;
;;; Factors!
;;;
;;;  Write a procedure that given a number it will return
;;;  a sentence of its factors.
;;;
;;;  After that, write a procedure to find the GCF
;;;  (greatest common factor), and a procedure to find
;;;  the LCM (least common multiple).
;;;
;;;  (I know gcd and lcm are already defined, but practice
;;;   writing it on your own)
;;;

(define (factors num)
  "")

(define (gcf x y)
  "")

(define (lcm x y)
  "")

;;;
;;; Pascal Row
;;;
;;;  Given a row number, write a procedure that returns the 
;;;  numbers in that row.
;;;
;;;  Example (pascal-row 2) -> (1 2 1)
;;;

(define (pascal-row row)
  "")

;;;
;;; Calculator
;;;
;;;  Given a sentence like (1 + 2 * 3 / 4 - 19), evaluate
;;;  the arithmetic expression in order (order of operations).
;;;
;;;  (Try doing it recursively and with HOF)
;;;  

(define (calc sent)
  "" )

;;;
;;; snack-n
;;;
;;;  Count the number of ways there are of eating n snacks.
;;;
;;;  (sent is a sentence of numbers representing snacks)

(define (snack-n sent)
  "")