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* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html.
*
* This file is a derivative of code released by the University of
* California under the terms listed below.
*
* Refinement Analysis Tools is Copyright (c) 2007 The Regents of the
* University of California (Regents). Provided that this notice and
* the following two paragraphs are included in any distribution of
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package com.ibm.wala.util.math;
import java.math.BigInteger;
/**
* Factorial utilities
*/
public class Factorial {
/** Factorial */
public static long fact(long n) {
long result = 1;
for (long i = 1; i <= n; i++)
result *= i;
return result;
}
/** Factorial */
public static BigInteger fact(BigInteger n) {
if (n == null) {
throw new IllegalArgumentException("n is null");
}
BigInteger result = BigInteger.ONE;
for (BigInteger i = BigInteger.ONE; i.compareTo(n) <= 0; i = i.add(BigInteger.ONE)) {
result = result.multiply(i);
}
return result;
}
/**
* Factorial on doubles; avoids overflow problems present when using integers.
*
* @param n arg on which to compute factorial
* @return (<code>double</code> approximation to) factorial of largest positive integer <= (n_ + epsilon)
*/
public static double fact(double n) {
n += 1e-6;
double result = 1.0;
for (double i = 1; i <= n; i += 1.0)
result *= i;
return result;
}
/** Factorial */
public static int fact(int n) {
int result = 1;
for (int i = 1; i <= n; i++)
result *= i;
return result;
}
}