having an issue with my perfect number function. The objective of the code is to determine if the number is a perfect number, meaning it is equal to the sum of its divisors. Ex:6. Im having trouble with my code. Here's my function:
(define (is-perfect x)
(define (divides a b) (= (modulo b a) 0))
(define (sum-proper-divisors y)
(if (= y 1)
1
(if (divides y x)
(+ y (sum-proper-divisors (- y 1)))
(if (= x 1)
#f
(= (sum-proper-divisors (- x 1)
x)))))))
You almost got it! there are a couple of problems, though. First, you're missing a case in sum-proper-divisors: you ask if y is one and if (divides y x), but what happens if y does not divide x?
The second problem, is that the last if expression must be outside of the definition of the two helper procedures, currently it's inside sum-proper-divisors. Properly indenting your code will make easier to find this kind of errors.
This is how a correct solution looks, because this looks like homework I'll let you fill-in the blanks:
(define (is-perfect x)
(define (divides a b)
(= (modulo b a) 0))
(define (sum-proper-divisors y)
(cond ((<= y 1)
1)
((divides y x)
(+ y (sum-proper-divisors (- y 1))))
(else
<???>))) ; what goes in here?
(if (= x 1)
#f
(= (sum-proper-divisors (- x 1)) x)))
