/*
 * Copyright 2007-2013
 * Licensed under GNU Lesser General Public License
 * 
 * This file is part of EpochX: genetic programming software for research
 * 
 * EpochX is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * EpochX is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with EpochX. If not, see <http://www.gnu.org/licenses/>.
 * 
 * The latest version is available from: http://www.epochx.org
 */
package org.epochx.epox.math;

import org.epochx.epox.Node;
import org.epochx.tools.*;

/**
 * A node which performs the common (base 10) logarithm, called LOG-10
 * 
 * @see Log
 * 
 * @since 2.0
 */
public class Log10 extends Node {

    public static final String IDENTIFIER = "LOG10";

	/**
	 * Constructs a Log10Function with one <code>null</code> child.
	 */
	public Log10() {
		this(null);
	}

	/**
	 * Constructs a Log10Function with one numerical child nodes.
	 * 
	 * @param child The child of which the base 10 logarithm will be calculated.
	 */
	public Log10(Node child) {
		super(child);
	}

	/**
	 * Evaluates this function. The child node is evaluated, the
	 * result of which must be of a numeric type (one of Byte,
	 * Short, Integer, Long). The base 10 logarithm is performed on this value
	 * and the result returned as a Double.
	 * 
	 * @return the base 10 logarithm performed on the value returned from the
	 * 			child
	 */
	@Override
	public Double evaluate() {
		double c = NumericUtils.asDouble(getChild(0).evaluate());

		return Math.log10(c);
	}

	/**
	 * Returns the identifier of this function which is LOG-10
	 * 
	 * @return this node's identifier
	 */
	@Override
	public String getIdentifier() {
		return IDENTIFIER;
	}

	/**
	 * Returns this function node's return type for the given child input types.
	 * If there is one input type of a numeric type then the return type will
	 * be Double. In all other cases this method will return <code>null</code>
	 * to indicate that the inputs are invalid.
	 * 
	 * @return the Double class or null if the input type is invalid.
	 */
	@Override
	public Class<?> dataType(Class<?> ... inputTypes) {
		if ((inputTypes.length == 1) && DataTypeUtils.isAllNumericType(inputTypes)) {
			return Double.class;
		}

		return null;
	}
}