/**
 *    Program:  Eval
 *    @author:  Paul Garrett, garrett@math.umn.edu
 *    @version: Sun Aug 15 17:31:00 CDT 1999
 *
 *    Purpose:  
 *
 */

//import lib.*;
import java.awt.*;

public class Eval extends java.applet.Applet {

	 TextField expressionField;
	 TextField valueOfXField;
	 TextField outField;
	 Tree tree;
	 Label evalLabel;
	 Button equalsButton;

	 public void init() {
		  expressionField = new TextField(30);
		  add(expressionField);
		  evalLabel = new Label("eval'd at");
		  add(evalLabel);
		  valueOfXField = new TextField(20);
		  add(valueOfXField);
		  equalsButton = new Button(" equals ");
		  add(equalsButton);
		  outField = new TextField(20);
		  add(outField);
	 }

	 public boolean action(Event e, Object ob) {
		  if (e.target == equalsButton) {
				double x0;
				try {
					 x0 = 
						  Double.valueOf( valueOfXField.getText() ).doubleValue();
				}
				catch (Exception ex) {
					 x0 = 0.0; // default ?
				}
				
				Tree tree = MathParser.stringToTree( expressionField.getText() );
				outField.setText("" + tree.eval(x0));
				return true;
		  }
		  return false;
	 }
    
}

/**************************************************
 *
 *   The End
 *
 ***************************************************/