import java.awt.*;
import java.lang.*;
import java.util.*;
import java.applet.Applet;

public class Calculator extends Applet {
    TextField Disp;	/* Display Area for inputs and results */
    Checkbox InvBox;	/* Inverse Function CheckBox */
    StringBuffer Expr;	/* String for the Number on Disp */
    Stack S1, S2;	/* Stacks for operands and operators */
    double memValue=0;	/* Memory Value */
    boolean newValue=true;

    public void init() {

	Expr = new StringBuffer();
	S1 = new Stack();
	S2 = new Stack();

	Panel CalTopPanel = new Panel();
	Panel CalBtmPanel = new Panel();

	setLayout(new GridLayout(0, 1, 20, 20));

	add(CalTopPanel);
	add(CalBtmPanel);

	CalTopPanel.setLayout(new GridLayout(0, 1, 20, 10));

	Panel CalDisPanel = new Panel();
        CalDisPanel.setFont(new Font("Helvetica", Font.PLAIN, 20));

	CalDisPanel.setLayout(new CardLayout());

	CalDisPanel.add(Disp = new TextField("0."));
	Disp.setEditable(false);
	Disp.setBackground(Color.white);
	Disp.setForeground(Color.blue);

	CalTopPanel.add(CalDisPanel);	/* Display Area */

	Panel CalNumPanel = new Panel();

	CalNumPanel.setLayout(new GridLayout(4, 3, 20, 15));
        CalNumPanel.setFont(new Font("Helvetica", Font.PLAIN, 14));
   
	/* Add number buttons */
	CalNumPanel.add(new Button("7"));
	CalNumPanel.add(new Button("8"));
	CalNumPanel.add(new Button("9"));
	CalNumPanel.add(new Button("4"));
	CalNumPanel.add(new Button("5"));
	CalNumPanel.add(new Button("6"));
	CalNumPanel.add(new Button("1"));
	CalNumPanel.add(new Button("2"));
	CalNumPanel.add(new Button("3"));
	CalNumPanel.add(new Button("0"));
	CalNumPanel.add(new Button("."));
	CalNumPanel.add(new Button("+/-"));

	Panel CalOprPanel = new Panel();

	CalOprPanel.setLayout(new GridLayout(0, 2, 20, 15));
        CalOprPanel.setFont(new Font("Helvetica", Font.PLAIN, 14));
   
	/* Add operator buttons */
	CalOprPanel.add(new Button("("));
	CalOprPanel.add(new Button(")"));
	CalOprPanel.add(new Button("*"));
	CalOprPanel.add(new Button("/"));
	CalOprPanel.add(new Button("+"));
	CalOprPanel.add(new Button("-"));
	CalOprPanel.add(new Button("="));
	CalOprPanel.add(new Button("1/X"));

	CalBtmPanel.setLayout(new GridLayout(0, 2, 20, 20));

	CalBtmPanel.add(CalNumPanel);
	CalBtmPanel.add(CalOprPanel);

	Panel CalMemPanel = new Panel();

	CalMemPanel.setLayout(new GridLayout(1, 0, 20, 20));
        CalMemPanel.setFont(new Font("Helvetica", Font.PLAIN, 14));
   
	/* Add memory buttons */
	CalMemPanel.add(new Button("MC"));
	CalMemPanel.add(new Button("MR"));
	CalMemPanel.add(new Button("M+"));
	CalMemPanel.add(new Button("M-"));

	Panel CalMthPanel = new Panel();

	CalMthPanel.setLayout(new GridLayout(1, 0, 20, 20));
        CalMthPanel.setFont(new Font("Helvetica", Font.PLAIN, 14));
   
	/* Add math function buttons */
	CalMthPanel.add(new Button("SIN"));
	CalMthPanel.add(new Button("COS"));
	CalMthPanel.add(new Button("X^2"));
	CalMthPanel.add(new Button("EXP"));

	Panel CalCtlPanel = new Panel();
        CalCtlPanel.setFont(new Font("Helvetica", Font.PLAIN, 14));

	CalCtlPanel.setLayout(new GridLayout(1,0,20,20));

	/* Add control buttons */
	CalCtlPanel.add(InvBox = new Checkbox("INV. F()"));
	CalCtlPanel.add(new Button("CA"));
	CalCtlPanel.add(new Button("C"));
	CalCtlPanel.add(new Button("Del"));

	CalTopPanel.add(CalCtlPanel);
	CalTopPanel.add(CalMthPanel);
	CalTopPanel.add(CalMemPanel);
    }/* end of init() */

    /* Uniary operation function */
    public boolean doUniary(Object arg) {
    
    double V1=0;
    int Op;
	
	Op = (((String)arg).charAt(0));
	V1 = Double.valueOf(Expr.toString()).doubleValue();
	if (InvBox.getState()) {
	switch(Op) {
	case '1':	/* 1/X */
	    V1 = 1.0 / V1;
	    break;
	case 'S':	/* ArcSin() */
	    V1 = (180.0/Math.PI)*Math.asin(V1);
	    break;
	case 'C':	/* ArcCos() */
	    V1 = (180.0/Math.PI)*Math.acos(V1);
	    break;
	case 'X':	/* Sqrt() */
	    V1 = Math.sqrt(V1);
	    break;
	case 'E':	/* Log() */
	    V1 = Math.log(V1);
	    break;
	}
	}
	else {
	switch(Op) {
	case '1':	/* 1/X */
	    V1 = 1.0 / V1;
	    break;
	case 'S':	/* Sin() */
	    V1 = Math.sin(V1*Math.PI/180.0);
	    break;
	case 'C':	/* Cos() */
	    V1 = Math.cos(V1*Math.PI/180.0);
	    break;
	case 'X':	/* X^2 */
	    V1 = V1*V1;
	    break;
	case 'E':	/* Exp() */
	    V1 = Math.exp(V1);
	    break;
	}
	}
	Expr.setLength(0); 
	Expr.append((new Double(V1)).toString());
	Disp.setText(Expr.toString());
	return true;
    }

    /* Binary operation function */
    public boolean doPostfix(int Op) {
    
	double V1=0, V2=0;
	
	if(!S1.empty())
	V1 = ((Double)S1.pop()).doubleValue();	/* Pop top operand */
	if(!S1.empty())
	V2 = ((Double)S1.pop()).doubleValue();	/* Pop second operand */
	switch(Op) {
	case '+':
	    V1 = V2 + V1;
	    break;
	case '-':
	    V1 = V2 - V1;
	    break;
	case '*':
	    V1 = V2 * V1;
	    break;
	case '/':
	    V1 = V2 / V1;
	    break;
	}
	S1.push(new Double(V1));	/* push result back to top of stack */
	Expr.setLength(0); 
	Expr.append((new Double(V1)).toString());
	Disp.setText(Expr.toString());	/* Display result */
	return true;
    }

    /* push operators and operands into two stacks according to precedence */
    public boolean doInfix(Object arg) {

    int Op;
	
	if("=".equals(arg)) {
	S1.push(Double.valueOf(Expr.toString()));
	while(!S2.empty()) {
	    Op = (((String)S2.peek()).charAt(0));
	    if ( Op == '(' ) return false;
	    Op = (((String)S2.pop()).charAt(0));
	    doPostfix(Op);
	}
	}
	else if("+".equals(arg)) {
	S1.push(Double.valueOf(Expr.toString()));
	while(!S2.empty()) {
	    Op = (((String)S2.peek()).charAt(0));
	    if ( Op == '(' ) break;
	    Op = (((String)S2.pop()).charAt(0));
	    doPostfix(Op);
	}
	S2.push(arg);
	}
	else if("-".equals(arg)) {
	S1.push(Double.valueOf(Expr.toString()));
	while(!S2.empty()) {
	    Op = (((String)S2.peek()).charAt(0));
	    if ( Op == '(' ) break;
	    Op = (((String)S2.pop()).charAt(0));
	    doPostfix(Op);
	}
	S2.push(arg);
	}
	else if("*".equals(arg)) {
	S1.push(Double.valueOf(Expr.toString()));
	while(!S2.empty()) {
	    Op = (((String)S2.peek()).charAt(0));
	    if ( Op == '(' || Op == '+' || Op == '-' ) break;
	    Op = (((String)S2.pop()).charAt(0));
	    doPostfix(Op);
	}
	S2.push(arg);
	}
	else if("/".equals(arg)) {
	S1.push(Double.valueOf(Expr.toString()));
	while(!S2.empty()) {
	    Op = (((String)S2.peek()).charAt(0));
	    if ( Op == '(' || Op == '+' || Op == '-' ) break;
	    Op = (((String)S2.pop()).charAt(0));
	    doPostfix(Op);
	}
	S2.push(arg);
	}
	else if("(".equals(arg)) {
	S2.push(arg);
	}
	else if(")".equals(arg)) {
	S1.push(Double.valueOf(Expr.toString()));
	while(!S2.empty()) {
	    Op = (((String)S2.pop()).charAt(0));
	    if ( Op == '(' ) break;
	    doPostfix(Op);
	}
	}
	return true;
    }

    public void clearAll() {
	while (!S1.empty())
	    S1.pop();
	while (!S2.empty())
	    S2.pop();
    }
    
    public boolean action(Event evt, Object arg) {
	if(evt.target instanceof Button) {
	/* binary operator buttons */
	    if("=".equals(arg) ||
	    "+".equals(arg) ||
	    "-".equals(arg) ||
	    "*".equals(arg) ||
	    "/".equals(arg) ||
	    "(".equals(arg) ||
	    ")".equals(arg)) {
	    doInfix(arg);
	    newValue=true;
	    }
	/* uniary operator buttons */
	    else if("1/X".equals(arg) ||
	    "SIN".equals(arg) ||
	    "COS".equals(arg) ||
	    "X^2".equals(arg) ||
	    "EXP".equals(arg)) {
	    doUniary(arg);
	    newValue=true;
	    }
	/* memory buttons */
	    else if("MC".equals(arg)) {
	    memValue=0;
	    newValue=true;
	    }
	    else if("MR".equals(arg)) {
	    Expr.setLength(0); 
	    Expr.append((new Double(memValue)).toString());
	    Disp.setText(Expr.toString());
	    }
	    else if("M+".equals(arg)) {
	    memValue+=Double.valueOf(Expr.toString()).doubleValue();
	    newValue=true;
	    }
	    else if("M-".equals(arg)) {
	    memValue-=Double.valueOf(Expr.toString()).doubleValue();
	    newValue=true;
	    }
	/* control buttons */
	    else if("CA".equals(arg)) {
	        Expr.setLength(0); 
	        Disp.setText(Expr.toString());
		newValue=true;
		clearAll();
	    }
	    else if("C".equals(arg)) {
	        Expr.setLength(0); 
	        Disp.setText(Expr.toString());
		newValue=true;
	    }
	    else if("Del".equals(arg)) {
	        if(Expr.length() > 0) {
		Expr.setLength(Expr.length()-1); 
		}
	        Disp.setText(Expr.toString());
	    }
	/* change sign button */
	    else if("+/-".equals(arg)) {
	        if(Expr.length() == 0 && newValue) {
		newValue=false;
		}
	        if(Expr.length() == 0 ||
		    ( Expr.charAt(0) != '-' && Expr.charAt(0) != ' ' ) ) {
		    Expr.insert(0,'-');
		}
	        else if( Expr.charAt(0) != '-' && Expr.charAt(0) == ' ' ) {
		    Expr.setCharAt(0,'-');
		}
		else {
		    Expr.setCharAt(0,' ');
		}
	        Disp.setText(Expr.toString());
	    }
	/* number buttons */
	    else {
		if(newValue) {
		newValue=false;
	        Expr.setLength(0); 
		}
	        Expr.append(arg.toString());
	        Disp.setText(Expr.toString());
	    }
	    return true;
	}
	return false;
    }

    public boolean keyDown(java.awt.Event evt, int key) {
    switch ((char) key) {
	/* number keys */
        case '0': case '1': case '2': case '3':
	case '4': case '5': case '6': case '7':
	case '8': case '9': case '.':
		if(newValue) {
		newValue=false;
	        Expr.setLength(0); 
		}
		Expr.append((char) key);
		Disp.setText(Expr.toString());
	break;
	/* binary operator keys */
        case '+': case '-': case '*': case '/': case '=':
        case '(': case ')':
	    doInfix(new String((new StringBuffer()).append((char) key)));
	    newValue=true;
	break;
	/* delete key and backspace key */
	case (char) 010: case (char) 0177:
	    if(Expr.length() > 0) {
	    Expr.setLength(Expr.length()-1); 
	    }
	    Disp.setText(Expr.toString());
	}
        return true;
    }

    public void paint(Graphics g) {
	Dimension d = size();
	g.drawRect(0, 0, d.width - 1, d.height - 1); /* Draw a box around */
    }

    public Insets insets() {
	return new Insets(10, 10, 10, 10);	/* Leave margin */
    }

    public Dimension PreferredSize() {
        return new Dimension(400, 400);
    }

    public static void main(String args[]) {
	Frame f = new Frame("Calculator");
	Calculator ex1 = new Calculator();

	ex1.init();

	f.add("Center", ex1);
	f.pack();
	f.resize(f.preferredSize());
	f.show();
    }
}