package umontreal.iro.lecuyer.randvar;
import umontreal.iro.lecuyer.rng.*;
import umontreal.iro.lecuyer.probdist.*;


/**
 * This class implements random variate generators for the Cauchy 
 * distribution. The density is
 * 

 * 
 * 

 * f (x) = β/(π[(x - α)2 + β2]) for  - ∞ < x < ∞,
 * 

 * where β > 0.
 * 
 * 

 * The (non-static) nextDouble method simply calls 
 * inverseF on the distribution.
 * 
 */
public class CauchyGen extends RandomVariateGen  {
   protected double alpha;
   protected double beta;



   /**
    * Creates a Cauchy random variate generator with parameters
    *   α = alpha and β = beta,
    *     using stream s.
    * 
    */
   public CauchyGen (RandomStream s, double alpha, double beta)  {
      super (s, new CauchyDist(alpha, beta));
      setParams(alpha, beta);
   }


   /**
    * Creates a Cauchy random variate generator with parameters
    *   α = 0 and β = 1, using stream s.
    * 
    */
   public CauchyGen (RandomStream s)  {
      this (s, 0.0, 1.0);
   }


   /**
    * Create a new generator for the distribution dist,
    *      using stream s.
    * 
    */
   public CauchyGen (RandomStream s, CauchyDist dist)  {
      super (s, dist);
      if (dist != null)
         setParams(dist.getAlpha(), dist.getBeta());
   }


   /**
    * Generates a new variate from the Cauchy distribution with parameters
    *  α = alpha and β = beta, using stream s.
    * 
    */
   public static double nextDouble (RandomStream s,
                                    double alpha, double beta) {
      return CauchyDist.inverseF (alpha, beta, s.nextDouble());
   }


   /**
    * Returns the parameter α of this object.
    * 
    */
   public double getAlpha() {
      return alpha;
   }


   /**
    * Returns the parameter β of this object.
    * 
    */
   public double getBeta() {
      return beta;
   }


   protected void setParams (double alpha, double beta) {
      if (beta <= 0.0)
         throw new IllegalArgumentException ("beta <= 0");
      this.alpha = alpha;
      this.beta = beta;
   }
}