// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2010-2011 Gael Guennebaud <gael.guennebaud@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
#ifndef EIGEN_TRANSPOSITIONS_H
#define EIGEN_TRANSPOSITIONS_H
namespaceEigen{
/** \class Transpositions
* \ingroup Core_Module
*
* \brief Represents a sequence of transpositions (row/column interchange)
*
* \param SizeAtCompileTime the number of transpositions, or Dynamic
* \param MaxSizeAtCompileTime the maximum number of transpositions, or Dynamic. This optional parameter defaults to SizeAtCompileTime. Most of the time, you should not have to specify it.
*
* This class represents a permutation transformation as a sequence of \em n transpositions
* \f$[T_{n-1} \ldots T_{i} \ldots T_{0}]\f$. It is internally stored as a vector of integers \c indices.
* Each transposition \f$ T_{i} \f$ applied on the left of a matrix (\f$ T_{i} M\f$) interchanges
* the rows \c i and \c indices[i] of the matrix \c M.
* A transposition applied on the right (e.g., \f$ M T_{i}\f$) yields a column interchange.
*
* Compared to the class PermutationMatrix, such a sequence of transpositions is what is
* computed during a decomposition with pivoting, and it is faster when applying the permutation in-place.
*
* To apply a sequence of transpositions to a matrix, simply use the operator * as in the following example:
* \code
* Transpositions tr;
* MatrixXf mat;
* mat = tr * mat;
* \endcode
* In this example, we detect that the matrix appears on both side, and so the transpositions
* are applied in-place without any temporary or extra copy.