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NAME
perm - permutation number
SYNOPSIS
perm(x, y)
TYPES
x int
y int
return int
DESCRIPTION
Return the permutation number P(x,y) which is defined as:
x!
--------
(x-y)!
This function computes the number of permutations in which y things
may be chosen from x items where order in which they are chosen matters.
EXAMPLE
; print perm(7,3), perm(7,4), perm(7,5), perm(3,0), perm(0,0)
210 840 2520 3 0
; print perm(2^31+1,3)
9903520314283042197045510144
LIMITS
x >= y >= 0
y < 2^24
LINK LIBRARY
void zperm(NUMBER x, y, *ret)
SEE ALSO
comb, fact, randperm
## Copyright (C) 1999-2006 Landon Curt Noll
##
## Calc is open software; you can redistribute it and/or modify it under
## the terms of the version 2.1 of the GNU Lesser General Public License
## as published by the Free Software Foundation.
##
## Calc 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 Lesser General
## Public License for more details.
##
## A copy of version 2.1 of the GNU Lesser General Public License is
## distributed with calc under the filename COPYING-LGPL. You should have
## received a copy with calc; if not, write to Free Software Foundation, Inc.
## 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
##
## Under source code control: 1994/10/20 04:03:02
## File existed as early as: 1994
##
## chongo <was here> /\oo/\ http://www.isthe.com/chongo/
## Share and enjoy! :-) http://www.isthe.com/chongo/tech/comp/calc/
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