/* file: pdf.H  Copyright glh 4/30/97 */
#ifndef PDFH
#define PDFH
#include <math.h>
#include <stdlib.h>
#include <iostream.h>
#include <assert.h>

typedef enum {false, true} Boolean;

class pdf {
  protected:
    const double MAX;   // (2**31)-1, random() --> [0,MAX]
    const double TWOPI; // 2*PI
  public:
    pdf() : MAX(2147483647.0), TWOPI(6.2831852) {} 
    void SetRand(int seed) {srandom(seed);}
    virtual double Draw()=0;
    virtual void Type()=0;
};

class uniform_pdf : public pdf {
//Returns a uniformly distributed random variable in the range [a,b].
  protected:
    double a,b;
  public:
    uniform_pdf(double arg1=0, double arg2=1) {a=arg1; b=arg2;}
    inline double Draw();
    void Type() {cout << "uniform, range [" << a << "," << b << "]";}
};

inline double uniform_pdf::Draw() {return ((b-a)/MAX * random() + a);}

class std_normal_pdf : public pdf {
//Returns a standard normal random variable. Uses the Box-Muller method.
  protected:
    Boolean one_left;
    double left_over;
  public:
    std_normal_pdf() {one_left=false;}
    double Draw();
    void Type() {cout << "standard normal";}
};

class normal_pdf : public pdf {
//Returns a normal random variable using a standard normal random variable. 
  protected:
    double mu, sigma;
  public:
    normal_pdf(double mean, double std_dev) {mu=mean; sigma=std_dev;}
    double Draw();
    void Type() {cout << "normal, mean=" << mu << ", standard deviation=" << sigma;}
};

class exponential_pdf : public pdf {
//Returns an exponentially distributed random variable. 
  protected:
    double mu;
  public:
    exponential_pdf(double mean) {mu = mean;}
    double Draw();
    void Type() {cout << "exponential, mean=" << mu;}
};

class erlang_pdf : public pdf {
//Returns an erlang distributed random variable. 
  protected:
    double k, mu;
  public:
    erlang_pdf(double param, double mean) {k = param; mu = mean;}
    double Draw();
    void Type() {cout << "erlang, mean=" << mu << " k=" << k;}
};

class Poisson_pdf : public pdf {
//Returns an Poisson distributed random variable.
  protected:
    double theta;
  public:
    Poisson_pdf(double mean) {theta = mean;}
    double Draw();
    void Type() {cout << "Poisson, mean and variance=" << theta;}
};

#endif