//<APPLET code="Anteisei.class"width=700 height=500></APPLET>

import java.applet.*;
import java.awt.*;
import java.awt.event.*;

public class Anteisei extends Applet implements ActionListener {
    
    //スクリーン
    private Image img;
    private Graphics gra;
    
    //ユーザーとのインターフェイス
    private double eps,q;
    private Label la1,la2;
    private TextField tf1,tf2;
    private Button bt1,bt2;
    private TextArea ta;
    
    //安定性解析の関数のためのパラメーター
    private double f;
    private double u,v; 
    private double a,b,c,d;
    private double tr_A,det_A,D;//線形化して出来た行列
    
    //二分法のためのパラメーター
    final private double EPS =1e-15;//打ち切り誤差
    final private int limit=50;//打ち切り回数
    private double low,mid,high;
    private int k=1;
    private double lastf,sol;
    
    //座標系の変換パラメーター
    private double ratiox,ratioy,X0,Y0;
    private int WX = 500, WY =500;

    //描画範囲
    private double x_max =   10;
    private double x_min =   -1;
    private double x_margin = (x_max-x_min)/10;
    private double y_max =  120;
    private double y_min =  -20;
    private double y_margin = (y_max-y_min)/10;

    private boolean IsIn(double x, double y) {
        return (x_min <= x && x <= x_max && y_min <= y && y <= y_max);
    }
    
    // 座標変換の準備
    private void space(double x0, double y0, double x1, double y1) {
        X0 = x0; Y0 = y0;
        ratiox = WX / (x1 - x0);
        ratioy = WY / (y1 - y0);
    }
    
    // ユーザー座標 (ワールド座標系) をウィンドウ座標 (デバイス座標系)
    private int wx(double x) {
        return (int)(ratiox * (x - X0));
    }
    // ユーザー座標 (ワールド座標系) をウィンドウ座標 (デバイス座標系)
    private int wy(double y) {
        return WY - (int)(ratioy * (y - Y0));
    }
    
    //tf からの数値読み取り
    private void ReadFields(){
        eps = Double.valueOf(tf1.getText()).doubleValue();
        q   = Double.valueOf(tf2.getText()).doubleValue();
    }
    
    //２乗の計算
    private double sqr(double x){
        return(x * x);
    }
    
    //判別式の関数 g1
    private double g1(double f){        
        
        u      = (1-f-q+Math.sqrt(sqr(f+q-1)+4*q*(1+f)))/2;
        v      = u;
        a      = (-2*u*u*u + (1 - 4 * q)*u*u + 2*q*(1-q)*u
                  + q*(q-2*f*v))/(eps*sqr(q+u));
        b      = f*(q-u)/(eps*(q+u));
        c      =  1;
        d      = -1;
        
        tr_A   = a + d;
        det_A  = a*d - b*c;
        D      = sqr(tr_A) - 4*det_A;
        
        return D;
    }
    
    //固有方程式の根の関数 g2
    private double g2(double f){
        
        u      = (1-f-q+Math.sqrt(sqr(f+q-1)+4*q*(1+f)))/2;
        v      = u;
        a      = (-2*u*u*u + (1 - 4 * q)*u*u + 2*q*(1-q)*u 
                  + q*(q-2*f*v))/(eps*sqr(q+u));
        b      = f*(q-u)/(eps*(q+u));
        c      =  1;
        d      = -1;
        
        tr_A   = a + d;
        det_A  = a*d - b*c;
        D      = sqr(tr_A) - 4*det_A;
        
        if(D>0)
            return (tr_A+Math.sqrt(D))/2;
        
        else
            return (tr_A)/2;
    }
    
    public void init() {
        
        //tf la bt のレイアウト
        setLayout(null);
        
        add(la1 = new Label("εの値:"));
        la1.setBounds (510,20,90,30);
        add(la2 = new Label("ｑの値:"));
        la2.setBounds (510,70,90,30);  
        add(tf1 = new TextField(""+1e-2)); 
        tf1.setBounds (610,20,80,30);
        add(tf2 = new TextField(""+8e-4)); 
        tf2.setBounds (610,70,80,30);
        
        //Startボタン
        add(bt1  = new Button("Start"));
        bt1.addActionListener(this);
        bt1.setBounds (610,140,80,30);
        
        //Clearボタン
        add(bt2  = new Button("Clear"));
        bt2.addActionListener(this);
        bt2.setBounds (610,190,80,30);
        
        //TextArea
        add(ta =new TextArea(5,7));
        ta.setBounds (510,280,180,220);
        
        //スクリーンの確保
        img=createImage(WX,WY);
        gra=img.getGraphics();
        gra.setColor(new Color(230,230,230));
        gra.fillRect(0,0,WX,WY);
        
        //座標軸とます目
        space(x_min-x_margin, y_min-y_margin
              , x_max+x_margin, y_max+y_margin);
        
        gra.setColor(Color.gray);
        for (double i=x_min; i<=x_max ; i=i+1){
            gra.drawLine(wx(i),wy(y_min),wx(i),wy(y_max));
        }
        for (double i=y_min; i<=y_max; i=i+10){
            gra.drawLine(wx(x_min),wy(i),wx(x_max),wy(i));
        }
        
        gra.setColor(Color.black);
        gra.drawLine(wx(x_min), wy(0.0), wx(x_max), wy(0.0));
        gra.drawLine(wx(0.0), wy(y_min), wx(0.0), wy(y_max));
        gra.drawString("0",wx(0.0),wy(0.0));
        gra.drawString("5",wx(5),wy(0.0));
        gra.drawString("10",wx(10),wy(0.0));
        
        gra.setColor(Color.blue);
        gra.drawString("判別式のグラフ",120,20);
        gra.drawString("5000",wx(-1),wy(50));
        gra.drawString("10000",wx(-1),wy(100));
        gra.setColor(Color.red);
        gra.drawString("固有値の実部の最大値のグラフ",220,20);
        gra.drawString("50",wx(0),wy(50));
        gra.drawString("100",wx(0),wy(100));
        
    }
    
    public void paint(Graphics g){
        update(g);
    }
    public void update(Graphics g){
        g.drawImage(img,0,0,this);
    }

    public void actionPerformed(ActionEvent e) {
        if(e.getSource() == bt1) {
            
            //一つ前の点と今の点
            double fx1,fx2;
            double fy1,fy2,fy3,fy4;
            
            //点を結ぶときの幅
            double delta1 = 5e-5;
            
            space(x_min-x_margin, y_min-y_margin
                  , x_max+x_margin, y_max+y_margin);
            ReadFields();
            
            for(f=0; f<=x_max; f=f+delta1) {
                
                fx1=f-delta1;
                fx2=f;
                fy1=g1(f-delta1)/100;
                fy2=g1(f)/100;
                fy3 = g2(f-delta1);
                fy4 = g2(f);
                
                //判別式のグラフの表示
                gra.setColor(Color.blue);
                if(IsIn(fx1,fy1) && IsIn(fx2,fy2)) {
                    gra.drawLine(wx(fx1),wy(fy1),wx(fx2),wy(fy2));
                    fx1=fx2;fy1=fy2;
                }
            
                //固有方程式の根のグラフの表示
                gra.setColor(Color.red);     
                if(IsIn(fx1,fy3) && IsIn(fx2,fy4)) {
                    gra.drawLine(wx(fx1),wy(fy3),wx(fx2),wy(fy4));
                    fx1=fx2;fy3=fy4;
                }
            }  
            
            repaint();
            
            double delta2 = 5e-2;
            
            //二分法による解の表示
            for(double x=0; x<=x_max; x=x+delta2){
                
                low=x;
                high=x+delta2;
                
                if( g1(low)*g1(high)<=0){
                    for (k=1;k<=limit;k++){
                        mid=(low+high)/2;
                        if(g1(low)*g1(mid)<0)
                            high=mid;
                        else
                            low=mid;
                        if(g1(mid)==0 || Math.abs(high-low)<Math.abs(low)*EPS){
                            sol=mid;
                            ta.setText(ta.getText()+lastf+"<f<"+sol+"\n"); 
                            
                            if(g1(low)<0){
                                ta.setText(ta.getText()+"渦あり");
                            }
                            else{
                                ta.setText(ta.getText()+"渦なし");
                            }
                            if(g2(low)<0){
                                ta.setText(ta.getText()+"安定"+"\n");
                            }
                            else{
                                ta.setText(ta.getText()+"不安定"+"\n");
                            }
                            
                            break;
                        }
                        lastf=sol;
                        
                        if(k>limit){
                            ta.setText(ta.getText()+"収束しない");
                        }
                    }
                }
                
                if ( g2(low)*g2(high)<=0){
                    for (k=1;k<=limit;k++){
                        mid=(low+high)/2;
                        if(g2(low)*g2(mid)<0)
                            high=mid;
                        else
                            low=mid;
                        if(g2(mid)==0 || Math.abs(high-low)<Math.abs(low)*EPS){
                            sol=mid;
                            ta.setText(ta.getText()+lastf+"<f<"+sol+"\n");
                            
                            if(g1(low)<0){
                                ta.setText(ta.getText()+"渦あり");
                            }
                            else{
                                ta.setText(ta.getText()+"渦なし");
                            }
                            if(g2(low)<0){
                                ta.setText(ta.getText()+"安定"+"\n");
                            }
                            else{
                                ta.setText(ta.getText()+"不安定"+"\n");
                            }
                            
                            break;
                        }
                        lastf=sol;
                        
                        if(k>limit){
                            ta.setText(ta.getText()+"収束しない");
                        }
                    }
                }
            }
            
            ta.setText(ta.getText()+sol+"<f"+"\n");
            
            if(g1(low)<0){
                ta.setText(ta.getText()+"渦あり");
            }
            else{
                ta.setText(ta.getText()+"渦なし");
            }
            if(g2(low)<0){
                ta.setText(ta.getText()+"安定"+"\n");
            }
            else{
                ta.setText(ta.getText()+"不安定"+"\n");
            }
            
            sol=0;
        }       
        
        //グラフの消去
        else if(e.getSource() == bt2){
            
            gra.setColor(new Color(230,230,230));
            gra.fillRect(0,0,WX,WY);
            
            space(x_min-x_margin, y_min-y_margin
                  , x_max+x_margin, y_max+y_margin);
           
            gra.setColor(Color.gray);
            for (double i=x_min; i<=x_max ; i=i+1){
                gra.drawLine(wx(i),wy(y_min),wx(i),wy(y_max));
            }
            for (double i=y_min; i<=y_max; i=i+10){
                gra.drawLine(wx(x_min),wy(i),wx(x_max),wy(i));
            }
            
            gra.setColor(Color.black);
            gra.drawLine(wx(x_min), wy(0.0), wx(x_max), wy(0.0));
            gra.drawLine(wx(0.0), wy(y_min), wx(0.0), wy(y_max));
            gra.drawString("0",wx(0.0),wy(0.0));
            gra.drawString("5",wx(5),wy(0.0));
            gra.drawString("10",wx(10),wy(0.0));
            
            gra.setColor(Color.blue);
            gra.drawString("判別式のグラフ",120,20);
            gra.drawString("5000",wx(-1),wy(50));
            gra.drawString("10000",wx(-1),wy(100));
            gra.setColor(Color.red);
            gra.drawString("固有値の実部の最大値のグラフ",220,20);
            gra.drawString("50",wx(0),wy(50));
            gra.drawString("100",wx(0),wy(100));

            repaint();
            
        }
    }
}