guile style

[jerry]

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)) )))