org.nfunk.jep.function
Class Binomial

java.lang.Object
  org.nfunk.jep.function.PostfixMathCommand
      org.nfunk.jep.function.Binomial

All Implemented Interfaces:

PostfixMathCommandI

public class Binomial
extends PostfixMathCommand

Binomial coeficients: binom(n,i). Requires n,i integers >=0. Often written nCi or column vector (n,i). (n,0) = 1, (n,1) = n, (n,n-1) = n, (n,n) = 1
(n,i) = n! / ( i! (n-i)! )
Pascals triangle rule: (n,i) = (n-1,i-1) + (n-1,i)
Binomial theorem: (a+b)^n = sum (n,i) a^i b^(n-i), i=0..n.

For efficiency the binomial coefficients are stored in a static array.

Author:

Rich Morris Created on 13-Feb-2005

Field Summary

Fields inherited from class org.nfunk.jep.function.PostfixMathCommand

curNumberOfParameters, numberOfParameters

Constructor Summary

Binomial()

Method Summary

static int	binom(int n, int i) Returns the binomial coefficients.
void	run(java.util.Stack s) Throws an exception because this method should never be called under normal circumstances.

Methods inherited from class org.nfunk.jep.function.PostfixMathCommand

checkNumberOfParameters, checkStack, getNumberOfParameters, setCurNumberOfParameters

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Binomial

public Binomial()

Method Detail

run

public void run(java.util.Stack s)
         throws ParseException

Description copied from class: PostfixMathCommand

Throws an exception because this method should never be called under normal circumstances. Each function should use it's own run() method for evaluating the function. This includes popping off the parameters from the stack, and pushing the result back on the stack.

Specified by:

run in interface PostfixMathCommandI

Overrides:

run in class PostfixMathCommand

Throws:

ParseException

binom

public static int binom(int n,
                        int i)
                 throws java.lang.ArrayIndexOutOfBoundsException

Returns the binomial coefficients.

Throws:

java.lang.ArrayIndexOutOfBoundsException - if n<0, i<0 or i>n