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Some folks might think: “you still use RCS”?!? And we will say, hey, at least we switched from SCCS to RCS back in … I think it was around 1994 ... at least we are keeping up! :-) :-) :-) Logs say that SCCS version 18 became RCS version 19 on 1994 March 18. RCS served us well. But now it is time to move on. And so we are switching to git. Calc releases produce a lot of file changes. In the 125 releases of calc since 1996, when I started managing calc releases, there have been 15473 file mods!
74 lines
2.5 KiB
Plaintext
74 lines
2.5 KiB
Plaintext
NAME
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factor - smallest prime factor not exceeding specified limit
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SYNOPSIS
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factor(n [, limit [, err]])
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TYPES
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n integer
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limit integer with abs(limit) < 2^32, defaults to 2^32 - 1
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err integer
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return positive integer or err
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DESCRIPTION
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This function ignores the signs of n and limit, so here we shall
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assume n and limit are both nonnegative.
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If n has a prime proper factor less than or equal to limit, then
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factor(n, limit) returns the smallest such factor.
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NOTE: A proper factor of n>1 is a factor < n. In other words,
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for n>1 is not a proper factor of itself. The value 1
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is a special case because 1 is a proper factor of 1.
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When every prime proper factor of n is greater than limit, 1 is
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returned. In particular, if limit < 2, factor(n, limit) always
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returns 1. Also, factor(n,2) returns 2 if and only if n is even
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and n > 2.
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If 1 < n < nextprime(limit)^2, then f(n, limit) == 1 <==> n is prime.
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For example, if 1 < n < 121, n is prime if and only if f(n,7) == 1.
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If limit >= 2^32, factor(n, limit) causes an error and
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factor(n, limit, err) returns the value of err.
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EXAMPLE
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; print factor(35,4), factor(35,5), factor(35), factor(-35)
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1 5 5 5
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; print factor(2^32 + 1), factor(2^47 - 1), factor(2^59 - 1)
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641 2351 179951
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LIMITS
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limit < 2^32
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LINK LIBRARY
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FLAG zfactor(ZVALUE n, ZVALUE limit, ZVALUE *res)
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SEE ALSO
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isprime, lfactor, nextcand, nextprime, prevcand, prevprime,
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pfact, pix, ptest
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## Copyright (C) 1999-2006 Landon Curt Noll
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##
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## Calc is open software; you can redistribute it and/or modify it under
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## the terms of the version 2.1 of the GNU Lesser General Public License
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## as published by the Free Software Foundation.
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##
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## Calc is distributed in the hope that it will be useful, but WITHOUT
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## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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## or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
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## Public License for more details.
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##
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## A copy of version 2.1 of the GNU Lesser General Public License is
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## distributed with calc under the filename COPYING-LGPL. You should have
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## received a copy with calc; if not, write to Free Software Foundation, Inc.
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## 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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##
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## Under source code control: 1995/12/18 12:34:57
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## File existed as early as: 1995
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##
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## chongo <was here> /\oo/\ http://www.isthe.com/chongo/
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## Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
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