Updated.

welcome-back-to-dr-racket/main.rkt~

@@ -1,32 +0,0 @@
-;; 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 main) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f () #f)))
-; List of Number -> String
-; Determines whether a list of 3 numbers is ascending or descending. Throws error if neither.
-(define (scending-how l)
-  (cond [(< (first l) (second l) (third l)) "ascending"]
-        [(> (first l) (second l) (third l)) "descending"]
-        [else (error "too complex")]))
-
-(check-expect (scending-how (list 1 2 3)) "ascending")
-(check-expect (scending-how (list 5 4 3)) "descending")
-(check-error (scending-how (list 1 0 3)))
-
-
-; Number, Number -> Number
-; Finds two positive numbers' greatest common denominator.
-(define (gcd2 a b)
-  (cond
-    [(= a 0) b]
-    [(= b 0) a]
-    [(= 0 (+ (modulo a 2) (modulo b 2))) (* 2 (gcd2 (/ a 2) (/ b 2)))]
-    [(= 0 (modulo b 2)) (gcd2 a (/ b 2))]
-    [(= 0 (modulo a 2)) (gcd2 (/ a 2) b)]
-    [else (if (<= a b) (gcd2 a (- b a)) (gcd2 b (- a b)))]))
-
-(check-expect (gcd2 0 0) 0)
-(check-expect (gcd2 100 0) 100)
-(check-expect (gcd2 10 2) 2)
-(check-expect (gcd2 10 10) 10)
-(check-expect (gcd2 14 7) 7)
-(check-expect (gcd2 288 64) 32)