source: trunk/source/global/management/src/G4Pow.cc @ 1340

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//
// $Id: G4Pow.cc,v 1.4 2010/08/24 08:12:08 gcosmo Exp $
// GEANT4 tag $Name: global-V09-03-22 $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4Pow
//
// Author:        Vladimir Ivanchenko
//
// Creation date: 23.05.2009
//
// -------------------------------------------------------------------

#include "G4Pow.hh"

G4Pow* G4Pow::fInstance = 0;

// -------------------------------------------------------------------

G4Pow* G4Pow::GetInstance()
{
  if (fInstance == 0)
  {
    static G4Pow manager;
    fInstance = &manager;
  }
  return fInstance;
}

// -------------------------------------------------------------------

G4Pow::G4Pow()
{
  const G4int maxZ = 256; 

  pz13.resize(maxZ,0.0);
  lz.resize(maxZ,0.0);
  fact.resize(maxZ,0.0);
  logfact.resize(maxZ,0.0);

  onethird = 1.0/3.0;
  G4double f = 1.0;

  for(G4int i=1; i<maxZ; ++i)
  {
    G4double x  = G4double(i);
    pz13[i] = std::pow(x,onethird);
    lz[i]   = std::log(x);
    f      *= x;
    fact[i] = f;
    logfact[i] = std::log(f);
  }
  fact[0] = 1.0;
  logfact[0] = 0.0;
}

// -------------------------------------------------------------------

G4Pow::~G4Pow()
{}

// -------------------------------------------------------------------

G4double G4Pow::powN(G4double x, G4int n)
{
  G4double res = 1.0;
  if(n >= 0) { for(G4int i=0; i<n; ++i) { res *= x; } }
  else if((n < 0) && (x != 0.0))
  {
    G4double y = 1.0/x;
    G4int nn = -n;
    for(G4int i=0; i<nn; ++i) { res *= y; }
  }
  return res;
}