/*------------------------------------------------------------------------------*
 * File Name: ComputeFactorial.c												*
 * Creation: ER, 01/26/05														*
 * Purpose: Programming Example													*
 * Copyright (c) OriginLab Corp.2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010	*
 * All Rights Reserved															*
 * 																				*
 * Modification Log:															*
 *------------------------------------------------------------------------------*/
 
#include <Origin.h>
#include <OC_nag8.h> // needed for nag_gamma function

/////////////////////////////////////////////////////////////////////////////////
// This example shows how to call a function from the NAG library to compute
// factorial.
//
// To view documentation on available NAG functions, look up the following section
// in the Programming Help File:
// Origin C Language Reference -> Global Functions -> NAG Functions
//
double compute_factorial(int n)
{
	// The NAG Gamma function returns (n-1)! when the argument n is an integer.
	// The function returns missing value if n is invalid (such as negative number)
	// or when n > 170.
	NagError fail;
	return nag_gamma(n + 1, &fail);
}
/////////////////////////////////////////////////////////////////////////////////