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// ProbabDistrib.h
// Declares the cProbabDistrib class representing a discrete probability distribution curve and random generator
/*
Usage:
1, Create a cProbabDistrib instance
2, Initialize the distribution either programmatically, using the SetPoints() function, or using a definition string
3, Ask for random numbers in that probability distribution using the Random() function
*/
#pragma once
// fwd:
class MTRand;
class cProbabDistrib
{
public:
class cPoint
{
public:
int m_Value;
int m_Probability;
cPoint(int a_Value, int a_Probability) :
m_Value(a_Value),
m_Probability(a_Probability)
{
}
} ;
typedef std::vector<cPoint> cPoints;
cProbabDistrib(int a_MaxValue);
/** Sets the distribution curve using an array of [value, probability] points, linearly interpolated. a_Points must not be empty. */
void SetPoints(const cPoints & a_Points);
/** Sets the distribution curve using a definition string; returns true on successful parse */
bool SetDefString(const AString & a_DefString);
/** Gets a random value from a_Rand, shapes it into the distribution curve and returns the value. */
int Random(MTRand & a_Rand) const;
/** Maps value in range [0, m_Sum] into the range [0, m_MaxValue] using the stored probability */
int MapValue(int a_OrigValue) const;
int GetSum(void) const { return m_Sum; }
protected:
int m_MaxValue;
/** Cumulative probability of the values, sorted, for fast bsearch lookup */
cPoints m_Cumulative;
/** Sum of all the probabilities across all values in the domain; -1 if not set */
int m_Sum;
} ;
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