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JEP is a Java library for parsing and evaluating mathematical expressions.

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/* @author rich
 * Created on 13-Feb-2005
 *
 * See LICENSE.txt for license information.
 */
package org.lsmp.djep.vectorJep.function;

import org.nfunk.jep.*;
import org.nfunk.jep.function.*;
import java.util.Stack;

import org.lsmp.djep.vectorJep.Dimensions;
import org.lsmp.djep.vectorJep.values.*;

/**
 * Returns the length of a vector. 
 * If the argument is a scaler, matrix or tensor returns total number of elements.
 *  * len(5) -> 1
 * len([1,2,3]) -> 3
 * len([[1,2],[3,4],[5,6]]) -> 6
 * 
 * @author Rich Morris
 * Created on 13-Feb-2005
 */
public class Length extends PostfixMathCommand implements UnaryOperatorI
{
	public Dimensions calcDim(Dimensions ldim)
	{
		return Dimensions.ONE;
	}

	public MatrixValueI calcValue(MatrixValueI res, MatrixValueI lhs)
		throws ParseException
	{
		int neles = lhs.getNumEles();
		res.setEle(0,new Integer(neles));
		return res;
	}

	public void run(Stack aStack) throws ParseException
	{
		Object obj = aStack.pop();
		MatrixValueI res = null;
		if(obj instanceof MatrixValueI)
		{
			res = Scaler.getInstance(new Integer(((MatrixValueI) obj).getNumEles()));
		}
		else
			res = Scaler.getInstance(new Integer(1));
		aStack.push(res);
	}

	public Length()
	{
		super();
		this.numberOfParameters = 1;
	}
}