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61 lines
1.7 KiB
Plaintext
61 lines
1.7 KiB
Plaintext
NAME
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perm - permutation number
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SYNOPSIS
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perm(x, y)
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TYPES
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x int
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y int
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return int
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DESCRIPTION
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Return the permutation number P(x,y) which is defined as:
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x!
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--------
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(x-y)!
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This function computes the number of permutations in which y things
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may be chosen from x items where order in which they are chosen matters.
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EXAMPLE
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; print perm(7,3), perm(7,4), perm(7,5), perm(3,0), perm(0,0)
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210 840 2520 3 0
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; print perm(2^31+1,3)
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9903520314283042197045510144
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LIMITS
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x >= y >= 0
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y < 2^24
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LINK LIBRARY
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void zperm(NUMBER x, y, *ret)
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SEE ALSO
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comb, fact, randperm
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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: 1994/10/20 04:03:02
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## File existed as early as: 1994
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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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