SICP 問題 3.37
(define (c+ x y) (let ((z (make-connector))) (adder x y z) z)) (define (c- x y) (let ((z (make-connector))) (adder x z y) z)) (define (c* x y) (let ((z (make-connector))) (multiplier x y z) z)) (define (c/ x y) (let ((z (make-connector))) (multiplier x z y) z)) (define (cv x) (let ((z (make-connector))) (constant x z) z))