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(add-to-load-path (dirname (current-filename)))
(import
(srfi srfi-41)
(extra-functional)
(my-streams))
(define base (stream-from 2))
(define (mark n item)
(if (eq? (remainder (car item) n) 0)
(cons (car item) #f)
item))
(define-stream (sieve input)
(stream-let loop ((strm (stream-map (part (flip cons) #t) input)))
(stream-match strm ((item . rest)
(if (cdr item)
(stream-cons
(car item)
(loop (stream-map (part mark (car item)) rest)))
(loop rest))))))
(define eratosthenes (sieve base))
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