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xt_n_choose_k(3)	   Library Functions Manual	      xt_n_choose_k(3)

NAME
       xt_n_choose_k() - Compute binomial coefficient N	choose K

LIBRARY
       #include	<xtend/math.h>
       -lxtend

SYNOPSIS
       #include	<stdint.h>
       #include	"math.h"
       unsigned	long   xt_n_choose_k(unsigned long n, unsigned long k)

ARGUMENTS
       n   Number of items to choose from
       k   Number of items chosen

DESCRIPTION
       Compute the binomial coefficient	N choose K = N!	/ (K! *	(N-K)!).  This
       represents  the	number	of  ways to choose K items out of a pool of N,
       such that we don't care about order.  E.g., if choosing 2 letters  from
       the set [A B C D	E], [C D] is considered	the same [D C].

       This  implementation avoids overflow by alternating multiply and	divide
       operations (rather than try to compute  factorials  first,  which  will
       fail for	relatively small values	of N or	K).

RETURN VALUES
       The number of ways to choose K items from N objects.

EXAMPLES
       #include	<xtend/math.h>

       unsigned	long   n = 5, k	= 2;

       printf("Ways to choose %lu items	from %lu = %lun",
	       k, n, xt_n_choose_k(n, k));

SEE ALSO
       lgamma(3)

							      xt_n_choose_k(3)

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