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


/**
 * This class implements random variate generators for the 
 * power distribution with shape parameter
 * c > 0, over the interval [a, b].
 * Its density is
 * 
 * 

 * 

 * f (x) = c(x - a)c-1/(b - a)c
 * 

 * for 
 * a <= x <= b, and 0 elsewhere.
 * 
 */
public class PowerGen extends RandomVariateGen  {
   private double a;
   private double b;
   private double c;


   /**
    * Creates a Power random variate generator with parameters
    *  a = a, b = b and c = c,
    *  using stream s.
    * 
    */
   public PowerGen (RandomStream s, double a, double b, double c)  {
      super (s, new PowerDist(a, b, c));
      setParams (a,  b, c);
   }


   /**
    * Creates a Power random variate generator with parameters
    *  a = 0, b = 1 and c = c, using stream s.
    * 
    */
   public PowerGen (RandomStream s, double c)  {
      super (s, new PowerDist(0.0, 1.0, c));
      setParams (0.0, 1.0, c);
   }


   /**
    * Creates a new generator for the power distribution dist
    *    and stream s.
    * 
    */
   public PowerGen (RandomStream s, PowerDist dist)  {
      super (s, dist);
      if (dist != null)
         setParams (dist.getA(), dist.getB(), dist.getC());
   } 


   /**
    * Uses inversion to generate a new variate from the power
    *    distribution with parameters a = a, b = b, and
    *    c = c, using stream s.
    * 
    */
   public static double nextDouble (RandomStream s, double a, double b,
                                    double c)  {
       return PowerDist.inverseF (a, b, c, s.nextDouble());
   }


   /**
    * Returns the parameter a.
    * 
    */
   public double getA() {
      return a;
   }


   /**
    * Returns the parameter b.
    * 
    */
   public double getB() {
      return b;
   }


   /**
    * Returns the parameter c.
    * 
    */
   public double getC() {
      return c;
   }


   /**
    * Sets the parameters a, b and c for this object.
    * 
    * 
    */
   public void setParams (double a, double b, double c)  {
      this.a  = a;
      this.b  = b;
      this.c  = c;
   }

}