public class function2D{
    private static final double zero=0.0e0;
    private int nx, Imethod, Degree;
    private double x[], y[], z[], x0, x1, dx;
    private boolean Constant;

    function2D(int nx, int Imethod, int Degree, boolean Constant, 
               double z[], double x0, double x1){
        setNx(nx);
        this.Imethod = Imethod;
        this.Degree = Degree;
        isConstant(Constant);
        this.z = z;
        this.x0 = x0; this.x1 = x1;
        setup();
        if(Imethod == 0)polynome();
        if(Imethod == 1)linear();
    }
    public void isConstant(boolean Constant)
    {
        this.Constant = Constant;
    }
    //Set the number of grid points, corresponding to the number
    //of (x, y) couples.
    public void setNx(int nx)
    {
        this.nx = nx;
    }
    public void setup()
    {
        x = new double[nx]; y = new double[nx];
        dx = x1 - x0;
        dx /= (nx-1);
    }
    public void polynome()
    {
        int i, k, n;
	
        if(Constant){
	      n = Degree+1;
	      for(i=0; i<nx; i++){
                x[i] = x0 + i*dx;
                for(y[i]=z[0], k=1; k<n; k++){
		        y[i] += z[k] * Math.pow(x[i], (double)k);
	          }
	      }
        }else{
	      n = Degree;
	      for(i=0; i<nx; i++){
                x[i] = x0 + i*dx;
	          for(y[i]=zero, k=1; k<=n; k++){
		        y[i] += z[k-1] * Math.pow(x[i], (double)k);
	          }
	      }
        }
        return;
    }
    public void linear()
    {
        int i;

        for(i=0; i<nx; i++){
            x[i] = x0 + i*dx;
	      y[i] = z[0] * x[i];
	      if(Constant)y[i] += z[1];
        }
        return;
    }
    public double[] GetX()
    {
        return(x);
    }
    public double[] GetY()
    {
        return(y);
    }
    public int getNx()
    {
        return(nx);
    }
}