# Exercise 1.30 of SICP

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:

(define (sum term a next b)
(define (iter a result)
(if <??>
<??>
(iter <??> <??>)))
(iter <??> <??>))


The iterative solution:

(define (sum term a next b)
(define (iter a result)
(if (> a b)
result
(iter (next a) (+ (term a) result))))
(iter a 0))