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(define-module (soe)
#:export (generate-primes-to
generate-initial-lst))
(define (generate-primes-to n)
(define (sieve buffer accept prev-size)
(if (or (null? buffer)
;; if filter removes nothing, we are done.
;; sub one because we always move an element into accepted
(eq? (length buffer) (1- prev-size)))
(append (reverse accept) buffer)
(let ((curr (car buffer))
(size (length buffer)))
(sieve
(filter
(lambda (x) (not (eq? (remainder x curr) 0)))
buffer)
(cons curr accept)
size))))
(let ((buffer (generate-initial-lst n))
(accept '(2)))
(if (> 2 n)
'()
(sieve buffer accept -1))))
(define (generate-initial-lst n)
"Generates a list of odd numbers
up to N."
(if (> 3 n)
'()
(iota (floor (/ (1- n) 2)) 3 2)))
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