Finding the antiderivative of a polynomial expression in Scheme

integration.ss

#lang scheme

(define (make-sum a1 a2) 
  (list '+ a1 a2))
(define (make-product m1 m2) 
  (list '* m1 m2))
(define (make-exponent e1 e2)
  (list '** e1 e2))

(define (term-integrate expr)
  (define (order term) (caddr (caddr term)))
  (define (var term) (cadr (caddr term)))
  (define (coeff term) (cadr term))
  (cond ((eq? (length expr) 0))
        (else (make-product 
               (/ (coeff expr) (+ (order expr) 1)) 
               (make-exponent (var expr) (+ (order expr) 1))))))

(define (integrate expr)
  (cond ((empty? expr) empty)
        (else (cons 
               (term-integrate (car expr))
               (integrate (cdr expr))))))