evaluatorjep.java

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/**    
  * Copyright (C) 2006, Laboratorio di Valutazione delle Prestazioni - Politecnico di Milano

  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.

  * This program 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 General Public License for more details.

  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */
  
package jmt.gui.exact.ld.eval;

import jmt.common.exception.ExpressionParseException;
import org.cheffo.jeplite.JEP;
import org.cheffo.jeplite.ParseException;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;

/**

 * @author alyf (Andrea Conti)
 * Date: 14-set-2003
 * Time: 16.26.42

 */

/**
 * an Evaluator using JEP by Nathan Funk
 * <a href="http://www.singularsys.com/jep">http://www.singularsys.com/jep</a>.
 */
public final class EvaluatorJep implements Evaluator {

	private JEP parser;
	private static final String X = "n";

    private String helpString;

	public EvaluatorJep() {
		parser = new JEP();
		parser.addStandardConstants();
		parser.addStandardFunctions();

        //custom functions can be added here with JEP.addFunction()

	}


    /**
     * Creates the help string, retrieving it from a html file.
     */
	private void loadHelp() {
		try {

            /*
            //OLD
            String helpFile = EvaluatorJep.class.getResource("EvaluatorJep.html").getPath();
            FileReader fr = new FileReader(new File(helpFile));

            char[] buf = new char[1024];
			StringBuffer s = new StringBuffer();
			int read;

			read = fr.read(buf);
			while (read > 0) {
				s.append(buf, 0, read);
				read = fr.read(buf);
			}
			fr.close();
			helpString = s.toString();

            */

			//String helpFile = EvaluatorJep.class.getResource("EvaluatorJep.html").getPath();

            URL url = EvaluatorJep.class.getResource("EvaluatorJep.html");
            InputStream inputStream = url.openStream();

			//FileReader fr = new FileReader(new File(helpFile));
            InputStreamReader fr = new InputStreamReader(inputStream);

            char[] buf = new char[1024];
			StringBuffer s = new StringBuffer();
			int read;

			read = fr.read(buf);
			while (read > 0) {
				s.append(buf, 0, read);
				read = fr.read(buf);
			}
			fr.close();
			helpString = s.toString();

        } catch (MalformedURLException e) {
            helpString = "JEP home page is at http://www.singularsys.com/jep";

		} catch (IOException e) {
            helpString = "JEP home page is at http://www.singularsys.com/jep";

		}
	}


	public double evaluate(String expression, double x) throws ExpressionParseException {
		parser.addVariable(X, x);
		parser.parseExpression(expression);
		if (parser.hasError()) {
			throw new ExpressionParseException(parser.getErrorInfo());
		}
        double val = 0;
        try {
            val = parser.getValue();
        } catch (ParseException e) {
            throw new ExpressionParseException(e.getMessage());
        }
        return val;
	}


	public double[] evaluate(String expression, double[] x) throws ExpressionParseException {
		double[] y = new double[x.length];
		evaluate(expression, x, y);
		return y;
	}

	public void evaluate(String expression, double[] x, double[] y) throws ExpressionParseException {
		if (x.length != y.length) throw new IllegalArgumentException("x and y must be the same length");
		for (int i = 0; i < x.length; i++) {
			y[i] = evaluate(expression, x[i]);
		}

	}


    //NEW
    //@author Stefano Omini
    public String getHelpText() {

        //load help from html
        loadHelp();
        return helpString;


    }
    //end NEW

}