sicp 2.2

sicp_2_2

(define (make-segment s e) (cons s e))
(define (start-segment x) (car x))
(define (end-segment x) (cdr x))
(define (midpoint-segment x) (/ (+ (start-segment x) (end-segment x)) 2))
(define (print-point p)
(newline)
(display "(")
(display (start-segment p))
(display ",")
(display (end-segment p))
(display ")"))

(print-point (make-segment -2 2))
(newline)
(midpoint-segment (make-segment -2 2))