#include "block.h"
#include "random.h"
#include "math.h"


class RandGauss :
      public Block
{
  private:
    OutPort < double > * out;
    Parameter < long > * seed;
    Parameter < double > * var;
    double stddevval;

    Random generator;

    double gset;          // im voraus berechnete Zahl
    bool iset;            // bereits eine Zufallszahl in voraus berechnet?


  public:
    RandGauss(const Blockopt & blockopt) : Block(blockopt)
    {}


    void makeParameters()
    {
      seed = new Parameter < long > (this, "seed", 12345);
      var = new Parameter < double > (this, "var", 1.);
    }


    void makeIOPorts()
    {
      out = new OutPort < double > (this, "out", 1);
    }


    void initialize()
    {
      iset = false;
      generator.setSeed(seed->value());
      stddevval = sqrt(var->value());
    }


    void go()
    {
      double fac, rsq, v1, v2;

      if (iset)
      {
        /* Already got one */
        iset = false;
        out->write(stddevval*gset);
      }
      else
      {
        // Generate TWO evenly distributed numbers between -1 and +1
        // that are inside the unit circle
        do
        {
          v1 = 2.0 * generator.getRand() - 1.;
          v2 = 2.0 * generator.getRand() - 1.;
          rsq = v1 * v1 + v2 * v2;
        }
        while (rsq >= 1.0 || rsq == 0.0);

        fac = sqrt( -2.0 * log(rsq) / rsq);
        gset = v1 * fac;
        iset = true;
        out->write(stddevval*v2*fac);
      }
    }
};


PUBLISH(RandGauss);