;; Previous, "Infix" version
(define (make-binop op left right)
(list left op right))
(define (binop? expression) (pair? expression))
(define (binop.left binop) (first binop))
(define (binop.op binop) (second binop))
(define (binop.right binop) (third binop))
;; New, "Prefix" version
(define (make-binop op left right)
(list op left right))
(define (binop? expression) (pair? expression))
(define (binop.left binop) (second binop))
(define (binop.op binop) (first binop))
(define (binop.right binop) (third binop))
(make-binop '+ 5 10)) ==> ????
