Code Review

Compare your solutions

    #| BEGIN (Write your solution here) |#
; Code from the book
(define (deriv exp var) (cond ((number? exp) 0) ((variable? exp) (if (same-variable? exp var) 1 0)) ((sum? exp) (make-sum (deriv (addend exp) var) (deriv (augend exp) var)))
((product? exp) (make-sum (make-product (multiplier exp) (deriv (multiplicand exp) var))
(make-product (deriv (multiplier exp) var) (multiplicand exp))))
(else (error "unknown expression type: DERIV" exp))))
(define (variable? x) (symbol? x))
(define (same-variable? v1 v2) (and (variable? v1) (variable? v2) (eq? v1 v2)))
(define (sum? x) (and (pair? x) (eq? (car x) '+)))
(define (addend s) (cadr s))
(define (product? x) (and (pair? x) (eq? (car x) '*)))
(define (multiplier p) (cadr p))
(define (=number? exp num) (and (number? exp) (= exp num)))
(define (make-product m1 m2) (cond ((or (=number? m1 0) (=number? m2 0)) 0) ((=number? m1 1) m2) ((=number? m2 1) m1) ((and (number? m1) (number? m2)) (* m1 m2)) (else (list '* m1 m2))))

; My code
(define (make-sum a1 a2) (cond ((=number? a1 0) a2) ((=number? a2 0) a1) ((and (number? a1) (number? a2)) (+ a1 a2))
(else (list '+ a1 a2))))

(define (augend s)
    (define (make-sum-list terms)
        (if (null? terms)
            0
            (let ((first (car terms)) (rest (cdr terms)))
                (make-sum first (make-sum-list rest))
            )
        )
    )
    (make-sum-list (cddr s))
)

(define (multiplicand p)
    (define (make-product-list terms)
        (if (null? terms)
            1
            (let ((first (car terms)) (rest (cdr terms)))
                (make-product first (make-product-list rest))
            )
        )
    )
    (make-product-list (cddr p))
)
#| END |#