import java.util.*;

//***********************************************************************************
/** Class to return iterate of Yorke map function.<br>
*/
//***********************************************************************************

public class YorkeFunction extends Map2DFunction {
      double X,Y;

      YorkeFunction() {      

            nParameters=2;    
            a = new double[nParameters];    
            aDefault = new double[nParameters];
            aDefault[0]=3.0;
            aDefault[1]=0.25; 
            title = "Yorke Map";
            xminDefault=0.0;
            xmaxDefault=1.0;
            yminDefault=-2.0; 
            ymaxDefault=2.0;
      }      
                       
      
//***********************************************************************************      
/** iterates the map function
* @param x input value
* @return iterated value
*/
//***********************************************************************************
      public void iterate(double[] x) {                       

            X = x[0];
            Y = x[1];
            x[0] = mod(a[0] * X);
            x[1] = a[1] * Y + Math.cos(2*Math.PI * X);
            x[2]=X;
            x[3]=Y;
      }      

//***********************************************************************************      
/** iterates the tangent space to the map
* @param x input value and returns updated values
* x[0] and x[1] contain the new values of X and Y
* x[2] and x[3] contain the previous values
* @param t value of tangent vector (updated by iteration)
*/
//***********************************************************************************
      public void iterateTangent(double[] x, double[] t) {             
      
            X = t[0];
            Y = t[1];
            t[0] = a[0] * X;
            t[1] = a[1] * Y - 2*Math.PI*Math.sin(2*Math.PI * x[0])*X;
      
      } 
//***********************************************************************************               
}