Mercurial > forge
view main/specfun/isprime.m @ 0:6b33357c7561 octave-forge
Initial revision
author | pkienzle |
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date | Wed, 10 Oct 2001 19:54:49 +0000 |
parents | |
children | 11e75f92a5db |
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## Copyright (C) 2000 Paul Kienzle ## ## This program is free software; you can redistribute it and/or modify ## it under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 2 of the License, or ## (at your option) any later version. ## ## This program is distributed in the hope that it will be useful, ## but WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ## GNU General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with this program; if not, write to the Free Software ## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA ## usage: isprime(n) ## Return true if n is a prime number, false otherwise. ## ## Something like the following is much faster if you need to test a lot ## of small numbers: ## t = ismember (n, primes (max (n (:)))); ## If max(n) is very large, then you should be using special purpose ## factorization code. ## ## See also: primes, factor, gcd, lcm function t = isprime(n) if !is_scalar(n) [nr, nc] = size(n); t = n; for i=1:nr for j=1:nc t(i,j) = isprime(t(i,j)); endfor endfor elseif (n != fix(n) || n < 2) t = 0; elseif n < 4 t = 1; else q = n./[2:sqrt(n)]; t = all (q != fix(q)); endif endfunction