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// -------------------------------------------------------------------
//      GEANT4 Class file
//
//
//      File name:     G4LegendrePolynomial
//
//      Author:        Jason Detwiler (jasondet@gmail.com)
// 
//      Creation date: February 2015
//
//      Modifications: 29 October 2024 Isaac Kunen
//      
//      Legendre Polynomial
//
// -------------------------------------------------------------------

#ifndef G4LEGENDREPOLYNOMIAL_HH
#define G4LEGENDREPOLYNOMIAL_HH

#include "globals.hh"
#include <vector>
#include <map>

class G4LegendrePolynomial
{
  public:
    // Access to coefficients
    static std::size_t GetNCoefficients(std::size_t order) { return order+1; }
    G4double GetCoefficient(std::size_t i, std::size_t order);

    // Evaluation functions
    G4double EvalLegendrePoly(G4int order, G4double x);

    G4double EvalAssocLegendrePoly(G4int l, G4int m, G4double x);

    // cache is not used; use EvalAssocLegendrePoly(l, m, x) instead.
    G4double EvalAssocLegendrePoly(G4int l, G4int m, G4double x,
      std::map<G4int, std::map<G4int, G4double> >* cache)
    {
      (void) cache; // suppress compiler warning for unused cache
      return EvalAssocLegendrePoly(l, m, x); 
    }

  protected: // Cache coefficients for speed
    void BuildUpToOrder(std::size_t order);
    std::vector< std::vector<G4double> > fCoefficients;
};

#endif