Package com.singularsys.jep.functions

Class Binomial

java.lang.Object

com.singularsys.jep.functions.PostfixMathCommand

com.singularsys.jep.functions.BinaryFunction

com.singularsys.jep.functions.Binomial

All Implemented Interfaces:

PostfixMathCommandI, java.io.Serializable

public class Binomial
extends BinaryFunction

Binomial coefficients: binom(n,i). Requires n,i integers >=0. Often written as nCi or column vector (n,i).

The following rules apply:
(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

See Also:

Serialized Form

Field Summary

Fields inherited from class com.singularsys.jep.functions.PostfixMathCommand

curNumberOfParameters, name, NaN, numberOfParameters

Constructor Summary

Constructors

Constructor	Description
Binomial()

Method Summary

Modifier and Type	Method	Description
static int	binom(int n, int i)	Returns the binomial coefficients. nCi.
java.lang.Object	eval(java.lang.Object l, java.lang.Object r)

Methods inherited from class com.singularsys.jep.functions.BinaryFunction

instanceOf, instanceOf, run

Methods inherited from class com.singularsys.jep.functions.PostfixMathCommand

asArray, asBool, asDouble, asInt, asLong, asStrictInt, asString, checkNumberOfParameters, getName, getNumberOfParameters, setCurNumberOfParameters, setName, toString, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

Binomial

public Binomial()

Method Detail

eval

public java.lang.Object eval(java.lang.Object l,
                             java.lang.Object r)
                      throws EvaluationException

Specified by:

eval in class BinaryFunction

Throws:

EvaluationException

binom

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

Returns the binomial coefficients. nCi.

Parameters:

n - n

i - i

Returns:

the binomial coefficient

Throws:

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