#ifndef __NormalDistribution_h_
#define __NormalDistribution_h_

/* Use this class to approximate the normal distribution curve.  The underlying
 * implementation is a binomial distribution with interpolation.  Use more
 * points to get a more precise answer.  1000 points can give an answer
 * accurate to within 0.01% of the correct answer.
 *
 * This class stores a table of values.  Creating the class takes longer than
 * an individual lookup.  You should only create the table once if you can
 * help it. */

class NormalDistribution
{
private:
  double *_points;
  double _mean;
  double _stdDev;
  int _max;
public:
  NormalDistribution(int numberOfPoints = 1000);
  ~NormalDistribution();
  double probability(double from, double to) const;  // Inputs are Z-scores.
  double probability(double to) const;  // From negative infinity.
};

#endif