;; 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-beginner-reader.ss" "lang")((modname week2_tu_full) (read-case-sensitive #t) (teachpacks ((lib "image.ss" "teachpack" "2htdp"))) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ((lib "image.ss" "teachpack" "2htdp")))))
(define (myif q a z)
  (cond [q a]
        [else z]))
  
;Design Recipe:
  
 ;Data
 ;Signature, Purpose Header
 ;Examples
 ;Body
 ;Tests (run the examples)

; addone : number -> number     <--- signature
; adds one to a number          <--- purpose
(define (addone n) ;<--- header
  (+ n 1))         ;<--- body

;Examples/Tests:
(check-expect (addone 4) 5)
(check-expect (addone -5) -4)

; Exam question 4: Use the design recipe to write a function
; projectx that projects a posn to x-axis.

; projectx : posn -> posn
; projects posn to the x-axis
(define (projectx p) 
  (make-posn (posn-x p) 0)
  )


(check-expect (projectx (make-posn 3 4))
              (make-posn 3 0))

(check-expect (projectx (make-posn -2 -6))
              (make-posn -2 0))

(check-expect (projectx (make-posn 4 0))
              (make-posn 4 0))