MultinomialIterator.java

/*
 * Copyright (c) 2013, SRI International
 * All rights reserved.
 * Licensed under the The BSD 3-Clause License;
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package com.sri.ai.util.math;

import java.util.Iterator;

import com.sri.ai.util.collect.EZIterator;

/**
 * An {@link Iterator} over {@link Multinomial}s.
 * Provided multinomial is internally kept by iterator and modifiable,
 * so operations on it will reflect on future operations with the iterator.
 */
public class MultinomialIterator extends EZIterator<Multinomial> {

	private Multinomial multinomial;
	
	/**
	 * Creates an iterator around a given multinomial.
	 * @param multinomial the multinomial to iterate
	 */
	public MultinomialIterator(Multinomial multinomial) {
		this.multinomial = multinomial;
		this.onNext = true;
		this.next = multinomial;
	}
	
	/**
	 * Creates an iterator around a multinomial constructed with {@link Multinomial#Multinomial(int, int)}.
	 * @param n the number of elements being distributed
	 * @param m the number of classes into which elements are being distributed
	 */
	public MultinomialIterator(int n, int m) {
		this(new Multinomial(n, m));
	}
	
	/**
	 * Creates an iterator around a multinomial constructed with {@link Multinomial#Multinomial(int[])}.
	 * @param counters an array of class counters to construct a multinomial from.
	 */
	public MultinomialIterator(int[] counters) {
		this(new Multinomial(counters));
	}
	
	@Override
	protected Multinomial calculateNext() {
		Multinomial result;
		boolean hasSuccessor = multinomial.iterate();
		if (hasSuccessor) {
			result = multinomial;
		}
		else {
			result = null;
		}
		return result;
	}
}