SICP 問題 2.46
(define (make-vect x y) (cons x y)) (define (xcor-vect v) (car v)) (define (ycor-vect v) (cdr v)) (define (add-vect v1 v2) (make-vect (+ (xcor-vect v1) (xcor-vect v2)) (+ (ycor-vect v1) (ycor-vect v2)))) (define (sub-vect v1 v2) (make-vect (- (xcor-vect v1) (xcor-vect v2)) (- (ycor-vect v1) (ycor-vect v2)))) (define (scale-vect s v) (make-vect (* s (xcor-vect v)) (* s (ycor-vect v))))