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


/**
 * This class implements a random variate generator for the 
 * geometric distribution. Its has parameter p and mass function
 * 
 * 

 * 

 * p(x) = p(1 - p)x for x = 0, 1, 2,...,
 * 

 * where 
 * 0 <= p <= 1.
 * Random variates are generated by calling inversion on the distribution object.
 * 
 */
public class GeometricGen extends RandomVariateGenInt  {
   private double p;



   /**
    * Creates a geometric random variate generator with
    *   parameter p, using stream s.
    * 
    */
   public GeometricGen (RandomStream s, double p)  {
      super (s, new GeometricDist(p));
      setParams (p);
   }


   /**
    * Creates a new generator for the distribution dist, using 
    *     stream s.
    * 
    */
   public GeometricGen (RandomStream s, GeometricDist dist)  {
      super (s, dist);
      if (dist != null)
         setParams (dist.getP());
   }
 
    
   public int nextInt () {
      return GeometricDist.inverseF (p, stream.nextDouble());
   }

   /**
    * Generates a geometric random variate with parameter
    *   p = p, using stream s, by inversion.
    * 
    */
   public static int nextInt (RandomStream s, double p)  {
      return GeometricDist.inverseF (p, s.nextDouble());
   }


   /**
    * Returns the parameter p of this object.
    * 
    * 
    */
   public double getP() {
      return p;
   }


   /**
    * Sets the parameter n and p of this object.
    * 
    */
   protected void setParams (double p) {
      if (p < 0.0 || p > 1.0)
         throw new IllegalArgumentException ("p not in range [0, 1]");
      this.p = p;
   }

}