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more/metanumeric.h

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//  Copyright (C) 2001  Petter Urkedal (petter.urkedal@matfys.lth.se)
//
//  This file is free software; you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation; either version 2 of the License, or
//  (at your option) any later version.
//
//  This file is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
//  As a special exception, you may use this file as part of a free
//  software library without restriction.  Specifically, if other files
//  instantiate templates or use macros or inline functions from this
//  file, or you compile this file and link it with other files to
//  produce an executable, this file does not by itself cause the
//  resulting executable to be covered by the GNU General Public
//  License.  This exception does not however invalidate any other
//  reasons why the executable file might be covered by the GNU General
//  Public License.
//
//  $Id: metanumeric.h,v 1.1 2002/05/30 22:52:07 petter_urkedal Exp $



#ifndef MORE_METANUMERIC_H
#define MORE_METANUMERIC_H

namespace more {

  template<int N> struct pow_;
  template<int N, int Selector>
    struct pow_helper_ {
        template<typename T>
          static T eval(T const& x) { return T(1)/pow_<-N>::eval(x); }
    };
  template<int N>
    struct pow_helper_<N, 1> {
        template<typename T>
          static T eval(T const& x) { return x*pow2(pow_<N/2>::eval(x)); }
    };
  template<int N>
    struct pow_helper_<N, 0> {
        template<typename T>
          static T eval(T const& x) { return pow2(pow_<N/2>::eval(x)); }
    };
  template<int N> struct pow_ : pow_helper_<N, (N%2 - (N<0)*2)> {};
  template<> struct pow_<0>
    { template<typename T> static T eval(T const& x) { return one; } };
  template<> struct pow_<1>
    { template<typename T> static T eval(T const& x) { return x; } };

  // Metaprogram to calculate X^Y for Y >= 0.

  template<int X, int Y> struct power_
    { static int const eval = X*power_<X, Y-1>::eval; };
  template<int X> struct power_<X, 0> { static int const eval = 1; };

  // Metaprogram to calculate X!/Y! for X >= Y, with default Y=0.
  // NOT TESTED
  template<int X, int Y=0> struct factorial_
    { static int const eval = X*factorial_<X-1, Y>::eval; };
  template<int X> struct factorial_<X, X> { static int const eval = 1; };

  // Binominal coefficients; pick out M from N.

  template<int N, int M> struct binominal_ {
      static int const eval
        = binominal_<N-1, M-1>::eval + binominal_<N-1, M>::eval;
  };
  template<int N> struct binominal_<N, 0> { static int const eval = 1; };
  template<int N> struct binominal_<N, N> { static int const eval = 1; };
  template<> struct binominal_<0, 0> { static int const eval = 1; };


} // more

#endif

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