Minor.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2006-2009 Benoit Jacob <jacob.benoit.1@gmail.com>
//
// 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_MINOR_H
#define EIGEN_MINOR_H

namespace Eigen { 

/**
  * \class Minor
  *
  * \brief Expression of a minor
  *
  * \param MatrixType the type of the object in which we are taking a minor
  *
  * This class represents an expression of a minor. It is the return
  * type of MatrixBase::minor() and most of the time this is the only way it
  * is used.
  *
  * \sa MatrixBase::minor()
  */

namespace internal {
template<typename MatrixType>
struct traits<Minor<MatrixType> >
 : traits<MatrixType>
{
  typedef typename nested<MatrixType>::type MatrixTypeNested;
  typedef typename remove_reference<MatrixTypeNested>::type _MatrixTypeNested;
  typedef typename MatrixType::StorageKind StorageKind;
  enum {
    RowsAtCompileTime = (MatrixType::RowsAtCompileTime != Dynamic) ?
                          int(MatrixType::RowsAtCompileTime) - 1 : Dynamic,
    ColsAtCompileTime = (MatrixType::ColsAtCompileTime != Dynamic) ?
                          int(MatrixType::ColsAtCompileTime) - 1 : Dynamic,
    MaxRowsAtCompileTime = (MatrixType::MaxRowsAtCompileTime != Dynamic) ?
                             int(MatrixType::MaxRowsAtCompileTime) - 1 : Dynamic,
    MaxColsAtCompileTime = (MatrixType::MaxColsAtCompileTime != Dynamic) ?
                             int(MatrixType::MaxColsAtCompileTime) - 1 : Dynamic,
    Flags = _MatrixTypeNested::Flags & (HereditaryBits | LvalueBit),
    CoeffReadCost = _MatrixTypeNested::CoeffReadCost // minor is used typically on tiny matrices,
      // where loops are unrolled and the 'if' evaluates at compile time
  };
};
}

template<typename MatrixType> class Minor
  : public MatrixBase<Minor<MatrixType> >
{
  public:

    typedef MatrixBase<Minor> Base;
    EIGEN_DENSE_PUBLIC_INTERFACE(Minor)

    inline Minor(const MatrixType& matrix,
                       Index row, Index col)
      : m_matrix(matrix), m_row(row), m_col(col)
    {
      eigen_assert(row >= 0 && row < matrix.rows()
          && col >= 0 && col < matrix.cols());
    }

    EIGEN_INHERIT_ASSIGNMENT_OPERATORS(Minor)

    inline Index rows() const { return m_matrix.rows() - 1; }
    inline Index cols() const { return m_matrix.cols() - 1; }

    inline Scalar& coeffRef(Index row, Index col)
    {
      return m_matrix.const_cast_derived().coeffRef(row + (row >= m_row), col + (col >= m_col));
    }

    inline const Scalar coeff(Index row, Index col) const
    {
      return m_matrix.coeff(row + (row >= m_row), col + (col >= m_col));
    }

  protected:
    const typename MatrixType::Nested m_matrix;
    const Index m_row, m_col;
};

/**
  * \return an expression of the (\a row, \a col)-minor of *this,
  * i.e. an expression constructed from *this by removing the specified
  * row and column.
  *
  * Example: \include MatrixBase_minor.cpp
  * Output: \verbinclude MatrixBase_minor.out
  *
  * \sa class Minor
  */
template<typename Derived>
inline Minor<Derived>
MatrixBase<Derived>::minor(Index row, Index col)
{
  return Minor<Derived>(derived(), row, col);
}

/**
  * This is the const version of minor(). */
template<typename Derived>
inline const Minor<Derived>
MatrixBase<Derived>::minor(Index row, Index col) const
{
  return Minor<Derived>(derived(), row, col);
}

} // end namespace Eigen

#endif // EIGEN_MINOR_H