1 ;; Exercise 1.30.  The sum procedure above generates a linear recursion. The procedure can be rewritten so that the sum is performed iteratively. Show how to do this by filling in the missing expressions in the following definition:
2 
3 (define (sum term a next b)
4   (define (iter a result)
5     (if (> a b)
6 	result
7 	(iter (next a) (+ (term a) result))))
8   (iter a 0))
9 
10 (define (integral f a b dx)
11   (define (add-dx x) (+ x dx))
12   (* (sum f (+ a (/ dx 2.0)) add-dx b)
13      dx))
14 
15 (define (cube x) (* x x x))
16 
17 (define (test-case actual expected)
18   (load-option 'format)
19   (newline)
20   (format #t "Actual: ~A Expected: ~A" actual expected))
21 
22 
23 
24 (test-case (integral cube 0.0 1.0 0.001) 0.25)