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

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/* @author rich
 * Created on 26-Feb-2004
 */

package org.lsmp.djepExamples;
import org.nfunk.jep.*;
import org.lsmp.djep.vectorJep.*;
/**
 * Examples using vectors and matricies
 */
public class VectorExample {
	static VectorJep j;
	
	public static void main(String args[])	{
		j = new VectorJep();
		j.addStandardConstants();
		j.addStandardFunctions();
		j.addComplex();
		j.setAllowUndeclared(true);
		j.setImplicitMul(true);
		j.setAllowAssignment(true);

		// parse and evaluate each equation in turn
		
		doStuff("[1,2,3]");               // Value: [1.0,2.0,3.0]
		doStuff("[1,2,3].[4,5,6]");       // Value: 32.0
		doStuff("[1,2,3]^^[4,5,6]");      // Value: [-3.0,6.0,-3.0]
		doStuff("[1,2,3]+[4,5,6]");       // Value: [5.0,7.0,9.0]
		doStuff("[[1,2],[3,4]]");         // Value: [[1.0,2.0],[3.0,4.0]]
		doStuff("[[1,2],[3,4]]*[1,0]");   // Value: [1.0,3.0]
		doStuff("[1,0]*[[1,2],[3,4]]");   // Value: [1.0,2.0]
		doStuff("[[1,2],[3,4]]*[[1,2],[3,4]]");   // Value: [[7.0,10.0],[15.0,22.0]]
		doStuff("x=[1,2,3]");             // Value: [1.0,2.0,3.0]
		doStuff("x+x");                   // Value: [2.0,4.0,6.0]
		doStuff("x.x");                 // Value: 14.0
		doStuff("x^x");                  // Value: [0.0,0.0,0.0]
		doStuff("ele(x,2)");              // Value: 2.0
		doStuff("y=[[1,2],[3,4]]");       // Value: [[1.0,2.0],[3.0,4.0]]
		doStuff("y * y");                 // Value: [[7.0,10.0],[15.0,22.0]]
		doStuff("ele(y,[1,2])");          // Value: 2.0
	}

	public static void doStuff(String str)	{
		try	{
			Node node = j.parse(str);
			Object value = j.evaluate(node);
			System.out.println(str + "\tvalue " + value.toString());
		}
		catch(ParseException e) { System.out.println("Parse error "+e.getMessage()); }		
		catch(Exception e) { System.out.println("evaluation error "+e.getMessage()); e.printStackTrace(); }		
	}
}