guile style

[jerry <jdinardo@nycap.rr.com>]

I am fairly new to guile and scheme. People tell me that I should use a 
functional style.

I have 3 solutions for project euler problem #1. The first is 
functional, the second is imperative and the third is written in "Little 
Schemer" style.

I was hoping other guile users would comment on preferences or the 
"correct way". Sorry in advance for any wrapping problems that may occur.

#!/usr/local/bin/guile  -s
!#
(use-modules (srfi srfi-1) (jpd stdio)) ;; for folds
(define N 1000)

(define ans
   (fold + 0
     (filter
       (lambda (x) (or (= 0 (modulo x 3)) (= 0 (modulo x 5))))
       (iota N))))
(print ans)

(define ans 0)
(for i N
   (if (or (= 0 (modulo i 3)) (= 0 (modulo i 5))) (set! ans (+ ans i))))
(print ans)

(define ans
   (let loop ((i 1) (ans 0))
     (cond
       ((>= i N) ans)
       ((or (= 0 (modulo i 3)) (= 0 (modulo i 5))) (loop (1+ i) (+ ans i)))
       (else (loop (1+ i) ans)) )))