Agree set! is not a desirable form. It is not consistently optimisable. I cannot find the reference in the manual.
Also consider the first form: you're building a list in 3 passes -- call iota to generate a list, call filter to navigate the list again, then fold to accumulate your answer. Therefore it's O(3N). The preferred form is definitely from the little schemer. On Sat, 19 Jun 2021, 8:56 am jerry, <jdina...@nycap.rr.com> wrote: > 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)) ))) > >
