Sieve of Eratosthenes: Difference between revisions

=={{header|Emacs Lisp}}==

<lang lisp>

(defun sieve-set (limit)

(let ((xs (make-vector (1+ limit) 0)))

(loop for i from 2 to limit

when (zerop (aref xs i))

collect i

and do (loop for m from (* i i) to limit by i

do (aset xs m 1)))))

</lang>

Straightforward implementation of [http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes#Implementation sieve of Eratosthenes], 2 times faster:

<lang lisp>

(defun sieve (limit)

(let ((xs (vconcat [0 0] (number-sequence 2 limit))))

(loop for i from 2 to (sqrt limit)

when (aref xs i)

do (loop for m from (* i i) to limit by i

do (aset xs m 0)))

(remove 0 xs)))

</lang>