sicp-2-1-1-rational-number-arithmetic

#lang racket

;;;;;;;;;
;; 2.1 ;;
;;;;;;;;;

(define (make-rat n d)
  (cond [(negative? d) (make-rat (- n) (- d))]
        [else
          (define g (gcd n d)) ; gcd always > 0
          (cons (/ n g) (/ d g))]))