Eigen/src/Core/Swap.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra. Eigen itself is part of the KDE project.
//
// Copyright (C) 2006-2008 Benoit Jacob <jacob@math.jussieu.fr>
//
// Eigen is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// Alternatively, 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.
//
// Eigen 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 Lesser General Public License or the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License and a copy of the GNU General Public License along with
// Eigen. If not, see <http://www.gnu.org/licenses/>.

#ifndef EIGEN_SWAP_H
#define EIGEN_SWAP_H

template <typename Derived, typename OtherDerived, bool IsVector = Derived::IsVectorAtCompileTime>
struct ei_swap_selector;

/** swaps *this with the expression \a other.
  *
  * \note \a other is only marked const because I couln't find another way
  * to get g++ (4.2 and 4.3) to accept that template parameter resolution.
  * The problem seems to be that when swapping expressions as in
  * m.row(i).swap(m.row(j)); the Row object returned by row(j) is a temporary
  * and g++ doesn't dare to pass it by non-constant reference.
  * It gets const_cast'd of course. TODO: get rid of const here.
  */
template<typename Derived>
template<typename OtherDerived>
void MatrixBase<Derived>::swap(const MatrixBase<OtherDerived>& other)
{
  MatrixBase<OtherDerived> *_other = const_cast<MatrixBase<OtherDerived>*>(&other);
  if(SizeAtCompileTime == Dynamic)
  {
    ei_swap_selector<Derived,OtherDerived>::run(derived(),other.const_cast_derived());
  }
  else // SizeAtCompileTime != Dynamic
  {
    typename Derived::Eval buf(*this);
    *this = other;
    *_other = buf;
  }
}

template<typename Derived, typename OtherDerived>
struct ei_swap_selector<Derived,OtherDerived,true>
{
  inline static void run(Derived& src, OtherDerived& other)
  {
    typename Derived::Scalar tmp;
    ei_assert(OtherDerived::IsVectorAtCompileTime && src.size() == other.size());
    for(int i = 0; i < src.size(); i++)
    {
      tmp = src.coeff(i);
      src.coeffRef(i) = other.coeff(i);
      other.coeffRef(i) = tmp;
    }
  }
};

template<typename Derived, typename OtherDerived>
struct ei_swap_selector<Derived,OtherDerived,false>
{
  inline void run(Derived& src, OtherDerived& other)
  {
    typename Derived::Scalar tmp;
    for(int j = 0; j < src.cols(); j++)
      for(int i = 0; i < src.rows(); i++)
      {
        tmp = src.coeff(i, j);
        src.coeffRef(i, j) = other.coeff(i, j);
        other.coeffRef(i, j) = tmp;
      }
  }
};

#endif // EIGEN_SWAP_H