// Estimatin of Roots by Exner Enterprises, C.2000
// Author: Nicholas Exner
// http://www.uiuc.edu/ph/www/exner
// Free to redistribute/publish/modify pending that
// the above comments are retained.

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.net.URL;
import java.util.*;

public class Bisection extends Applet {
	Image offscreenImage;
	Graphics h;
	double a=0.0,b=0.0;
	String S_formula;
	String key;

	Label label_a = new Label("A: ");
	Label label_b = new Label("B: ");
	Label label_c = new Label("Formula: ");
	TextField inputA;
	TextField inputB;
	TextField inputC;

  	TextArea ta = new TextArea("Ready...",15,40);

      StringBuffer buf;

	Button calculate = new Button("Calculate");
      Choice d= new Choice();

   public void init(){

	inputA = new TextField(3);
	inputB = new TextField(3);
	inputC = new TextField(10);

      d.addItem("Bisection");
      d.addItem("False Position");
	d.addItem("Secant");
	d.addItem("Newton");

	add(label_a);
	add(inputA);
	add(label_b);
	add(inputB);

	add(label_c);
	add(inputC);

	add(d);
	add(calculate);

	add(ta);

	key = "Bisection";
	buf = new StringBuffer();
	setBackground(Color.white);
	repaint();
   }

   public void paint(Graphics g) {
	// Paint Nothing
   }

   public boolean mouseUp(Event evt, int x, int y) {
	return true;
   }
   public void processButton() {
		buf = new StringBuffer();	//Clean off buffer

		double aa = 0.0;
		double bb = 0.0;
		String spacedString="";
	try {
		aa = Double.valueOf(inputA.getText()).doubleValue();
		bb = Double.valueOf(inputB.getText()).doubleValue();
		spacedString = inputC.getText();
        } catch (NumberFormatException e) { }


		S_formula = "";
		for (int i=0;i < spacedString.length();i++) {
			if (spacedString.charAt(i) != ' ')
				S_formula += spacedString.charAt(i);
		}
					
		if (key.equals("Bisection")) {
			bisection(aa,bb);
		}
		if (key.equals("False Position")) {
			falsePosition(aa,bb);
		}
		if (key.equals("Secant")) {
			secant(aa,bb);
		}
		if (key.equals("Newton")) {
			newton(aa,bb);
		}

		System.out.println("Button Pressed");
	     	ta.setText(buf.toString());
   } //End Processbutton

   public boolean action (Event evt, Object arg) {
	if (evt.target instanceof Button) {
		processButton();
	}
      if (evt.target instanceof Choice){
            key=(String)arg;
      }
	return true;
   }

   public void update(Graphics g) {
	paint(g);
   }

   public void bisection(double a,double b) {
	double m = 0.0;
	while (Math.abs(b-a) > .00001) {
		buf.append("A: "+a+" \tB: "+b+"\n");

		System.out.println("A: "+a+" B: "+b);
		m = (a+b)/2;

		// Check to see if root was hit at midpoint
		if (f(m) == 0) {
			a=m;
			b=m;
		} else if (f(a)*f(m)< 0) {
			b=m;
		} else {
			a=m;
		}
	} // End while
	buf.append("approximate root is "+((b-a)/2));
   } // End Bisection

   public void falsePosition(double a,double b) {
	double xold = a, 
		 xn = b, 
		 m =0.0;

	while (Math.abs(xold-xn) > .00001) {
		xold = xn;
		buf.append("A: "+a+" \tB: "+b+"\n");
		m = (a*f(b)-b*f(a))/(f(b)-f(a));

		// Check to see if root was hit
		if (f(m) == 0) {
			a=m;
			b=m;
		} else if (f(a)*f(m)< 0) {
			b=m;
		} else {
			a=m;
		}
		xn=m;
	} // End while			
	buf.append("approximate root is "+xn);
   } // End False Position

   public void newton(double a,double b) {
	double xn = 0.0, 
		
		 n = 0.0001,
		 xi = a;
		buf.append("A: "+f(xi)+"\n");
		xn = xi-(f(xi)/fdx(xi));

	while (Math.abs(xn-xi) > .00001) {
		buf.append("A: "+f(xn)+"\n");
		xi=xn;
		xn= xi-(f(xi)/fdx(xi));
	} // End while			
	buf.append("approximate root is "+xn);
   } // End Newton

   public void secant(double a,double b) {
	double xold = a, 
		 xn = b, 
		 m =0.0;

	while (Math.abs(a-b) > .00001) {
		m = (a*f(b)-b*f(a))/(f(b)-f(a));
		a=b;
		b=m;
		buf.append("A: "+a+" \tB: "+b+"\n");
	} // End while			
	buf.append("approximate root is "+b);
   } // End Secant

public double f(double x) {
	String s = S_formula,
		 tempNum = "",
		 tempNum2= "";
	double total=0.0;
	boolean addStat = true;

	for (int i=0; i < s.length();i++) {

		if (isNum(s,i)){
			tempNum+=s.charAt(i);
		}	
		if (s.charAt(i) == 'x'){
			double totalTemp;
			// Get coefficient
			double temp=1;
			if (!tempNum.equals("")){
				temp = Double.valueOf(tempNum).doubleValue();
				tempNum="";
			}
			i++;
			if (i<s.length() && s.charAt(i)== '^'){
				tempNum2="";
				i++;
				while (i<s.length() && isNum(s,i)) {
					tempNum2+=s.charAt(i);
					i++;
				}
				double temp3=1;
				if (!tempNum2.equals("")){
				 	temp3= Double.valueOf(tempNum2).doubleValue();
				}
				totalTemp = Math.pow(x,temp3);
			} else {
				totalTemp = x;
			} // End ^
			if (addStat)
				total+=totalTemp*temp;
			else
				total-=totalTemp*temp;
		} // End x
		if (i < s.length() && s.charAt(i) == '+'){
			if (!tempNum.equals("")){
				double temp = Double.valueOf(tempNum).doubleValue();
				if (addStat)
					total+= temp;
				else
					total-= temp;
			}
			tempNum="";
			addStat=true;
		}
		if (i < s.length() && s.charAt(i) == '-'){
			if (!tempNum.equals("")){
				double temp = Double.valueOf(tempNum).doubleValue();
				if (addStat)
					total+= temp;
				else
					total-= temp;
			}	
			tempNum="";	
			addStat=false;	
		}
	} //End String search

	// Process last numbers
	if (!tempNum.equals("")){
		double temp = Double.valueOf(tempNum).doubleValue();
		if (addStat)
			total+= temp;
		else
			total-= temp;
	}
	return total;
}

public double fdx(double x) {
	double total=0.0;
	double totalTemp=0.0;
	String s = S_formula;
	String tempNum="";
	String tempNum2="";
	int numberOfX=0;
	double temp=0;
	boolean addStat=true;

	for (int i=0;i<s.length();i++) {
		if (s.charAt(i) == 'x'){
			// Get coefficient
			if (!tempNum.equals("")){
				temp = Double.valueOf(tempNum).doubleValue();
				tempNum="";
			} else {
				temp=1;
			}

			if ((i+1)<s.length() && s.charAt(i+1)== '^'){
				int ir=2;
				tempNum2="";

				while ((i+ir)<s.length() && isNum(s,(i+ir))) {
					tempNum2+=s.charAt(i+ir);
					ir++;
				}
				int temp3;
				if (!tempNum2.equals("")){
				 	temp3= Integer.parseInt((String)tempNum2);
				} else
					temp3 = 1;

				totalTemp = temp3*Math.pow(x,(temp3-1));
			} else {
				totalTemp = 1;
			}
			if (addStat)
				total+=totalTemp*temp;
			else
				total-=totalTemp*temp;
		} // End if on x

		if (isNum(s,i)){
			tempNum+=s.charAt(i);
		}
		if (s.charAt(i) == '+'){
			addStat=true;
			tempNum="";
		}
		if (s.charAt(i) == '-'){
			addStat=false;
			tempNum="";
		}
	} // End For
	System.out.println("Evaluated: "+total);
	return total;
} //End fdx


	public boolean isNum(String s,int i) {	
		if (s.charAt(i) >= '0' && (s.charAt(i)<= '9')) {
			return true;
		} else
			return false;
	}
} // End class Bisection