Eigen/src/Core/CoreEvaluators.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2011 Benoit Jacob <jacob.benoit.1@gmail.com>
// Copyright (C) 2011 Gael Guennebaud <gael.guennebaud@inria.fr>
// Copyright (C) 2011-2012 Jitse Niesen <jitse@maths.leeds.ac.uk>
//
// 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_COREEVALUATORS_H
#define EIGEN_COREEVALUATORS_H

namespace Eigen {

namespace internal {

// evaluator_traits<T> contains traits for evaluator_impl<T> 

template<typename T>
struct evaluator_traits
{
  // 1 if evaluator_impl<T>::evalTo() exists
  // 0 if evaluator_impl<T> allows coefficient-based access
  static const int HasEvalTo = 0;

  // 1 if assignment A = B assumes aliasing when B is of type T and thus B needs to be evaluated into a
  // temporary; 0 if not.
  static const int AssumeAliasing = 0;
};

// expression class for evaluating nested expression to a temporary
 
template<typename ArgType>
class EvalToTemp;

// evaluator<T>::type is type of evaluator for T
// evaluator<T>::nestedType is type of evaluator if T is nested inside another evaluator
 
template<typename T>
struct evaluator_impl 
{ };
 
template<typename T, int Nested = evaluator_traits<T>::HasEvalTo>
struct evaluator_nested_type;

template<typename T>
struct evaluator_nested_type<T, 0>
{
  typedef evaluator_impl<T> type;
};

template<typename T>
struct evaluator_nested_type<T, 1>
{
  typedef evaluator_impl<EvalToTemp<T> > type;
};

template<typename T>
struct evaluator
{
  typedef evaluator_impl<T> type;
  typedef typename evaluator_nested_type<T>::type nestedType;
};

// TODO: Think about const-correctness

template<typename T>
struct evaluator<const T>
  : evaluator<T>
{ };

// ---------- base class for all writable evaluators ----------

// TODO this class does not seem to be necessary anymore
template<typename ExpressionType>
struct evaluator_impl_base
{
  typedef typename ExpressionType::Index Index;
  // TODO that's not very nice to have to propagate all these traits. They are currently only needed to handle outer,inner indices.
  typedef traits<ExpressionType> ExpressionTraits;

  evaluator_impl<ExpressionType>& derived() 
  {
    return *static_cast<evaluator_impl<ExpressionType>*>(this); 
  }
};

// -------------------- Matrix and Array --------------------
//
// evaluator_impl<PlainObjectBase> is a common base class for the
// Matrix and Array evaluators.

template<typename Derived>
struct evaluator_impl<PlainObjectBase<Derived> >
  : evaluator_impl_base<Derived>
{
  typedef PlainObjectBase<Derived> PlainObjectType;

  enum {
    IsRowMajor = PlainObjectType::IsRowMajor,
    IsVectorAtCompileTime = PlainObjectType::IsVectorAtCompileTime,
    RowsAtCompileTime = PlainObjectType::RowsAtCompileTime,
    ColsAtCompileTime = PlainObjectType::ColsAtCompileTime
  };

  evaluator_impl(const PlainObjectType& m) 
    : m_data(m.data()), m_outerStride(IsVectorAtCompileTime ? 0 : m.outerStride()) 
  { }

  typedef typename PlainObjectType::Index Index;
  typedef typename PlainObjectType::Scalar Scalar;
  typedef typename PlainObjectType::CoeffReturnType CoeffReturnType;
  typedef typename PlainObjectType::PacketScalar PacketScalar;
  typedef typename PlainObjectType::PacketReturnType PacketReturnType;

  CoeffReturnType coeff(Index row, Index col) const
  {
    if (IsRowMajor)
      return m_data[row * m_outerStride.value() + col];
    else
      return m_data[row + col * m_outerStride.value()];
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_data[index];
  }

  Scalar& coeffRef(Index row, Index col)
  {
    if (IsRowMajor)
      return const_cast<Scalar*>(m_data)[row * m_outerStride.value() + col];
    else
      return const_cast<Scalar*>(m_data)[row + col * m_outerStride.value()];
  }

  Scalar& coeffRef(Index index)
  {
    return const_cast<Scalar*>(m_data)[index];
  }

  template<int LoadMode> 
  PacketReturnType packet(Index row, Index col) const
  {
    if (IsRowMajor)
      return ploadt<PacketScalar, LoadMode>(m_data + row * m_outerStride.value() + col);
    else
      return ploadt<PacketScalar, LoadMode>(m_data + row + col * m_outerStride.value());
  }

  template<int LoadMode> 
  PacketReturnType packet(Index index) const
  {
    return ploadt<PacketScalar, LoadMode>(m_data + index);
  }

  template<int StoreMode> 
  void writePacket(Index row, Index col, const PacketScalar& x)
  {
    if (IsRowMajor)
      return pstoret<Scalar, PacketScalar, StoreMode>
	            (const_cast<Scalar*>(m_data) + row * m_outerStride.value() + col, x);
    else
      return pstoret<Scalar, PacketScalar, StoreMode>
                    (const_cast<Scalar*>(m_data) + row + col * m_outerStride.value(), x);
  }

  template<int StoreMode> 
  void writePacket(Index index, const PacketScalar& x)
  {
    return pstoret<Scalar, PacketScalar, StoreMode>(const_cast<Scalar*>(m_data) + index, x);
  }

protected:
  const Scalar *m_data;

  // We do not need to know the outer stride for vectors
  variable_if_dynamic<Index, IsVectorAtCompileTime  ? 0 
                                                    : int(IsRowMajor) ? ColsAtCompileTime 
                                                    : RowsAtCompileTime> m_outerStride;
};

template<typename Scalar, int Rows, int Cols, int Options, int MaxRows, int MaxCols>
struct evaluator_impl<Matrix<Scalar, Rows, Cols, Options, MaxRows, MaxCols> >
  : evaluator_impl<PlainObjectBase<Matrix<Scalar, Rows, Cols, Options, MaxRows, MaxCols> > >
{
  typedef Matrix<Scalar, Rows, Cols, Options, MaxRows, MaxCols> XprType;

  evaluator_impl(const XprType& m) 
    : evaluator_impl<PlainObjectBase<XprType> >(m) 
  { }
};

template<typename Scalar, int Rows, int Cols, int Options, int MaxRows, int MaxCols>
struct evaluator_impl<Array<Scalar, Rows, Cols, Options, MaxRows, MaxCols> >
  : evaluator_impl<PlainObjectBase<Array<Scalar, Rows, Cols, Options, MaxRows, MaxCols> > >
{
  typedef Array<Scalar, Rows, Cols, Options, MaxRows, MaxCols> XprType;

  evaluator_impl(const XprType& m) 
    : evaluator_impl<PlainObjectBase<XprType> >(m) 
  { }
};

// -------------------- EvalToTemp --------------------

template<typename ArgType>
struct traits<EvalToTemp<ArgType> >
  : public traits<ArgType>
{ };

template<typename ArgType>
class EvalToTemp
  : public dense_xpr_base<EvalToTemp<ArgType> >::type
{
 public:
 
  typedef typename dense_xpr_base<EvalToTemp>::type Base;
  EIGEN_GENERIC_PUBLIC_INTERFACE(EvalToTemp)
 
  EvalToTemp(const ArgType& arg)
    : m_arg(arg)
  { }
 
  const ArgType& arg() const
  {
    return m_arg;
  }

  Index rows() const 
  {
    return m_arg.rows();
  }

  Index cols() const 
  {
    return m_arg.cols();
  }

 private:
  const ArgType& m_arg;
};
 
template<typename ArgType>
struct evaluator_impl<EvalToTemp<ArgType> >
{
  typedef EvalToTemp<ArgType> XprType;
  typedef typename ArgType::PlainObject PlainObject;

  evaluator_impl(const XprType& xpr) 
    : m_result(xpr.rows(), xpr.cols()), m_resultImpl(m_result)
  {
    // TODO we should simply do m_result(xpr.arg());
    call_dense_assignment_loop(m_result, xpr.arg());
  }

  // This constructor is used when nesting an EvalTo evaluator in another evaluator
  evaluator_impl(const ArgType& arg) 
    : m_result(arg.rows(), arg.cols()), m_resultImpl(m_result)
  {
    // TODO we should simply do m_result(xpr.arg());
    call_dense_assignment_loop(m_result, arg);
  }

  typedef typename PlainObject::Index Index;
  typedef typename PlainObject::Scalar Scalar;
  typedef typename PlainObject::CoeffReturnType CoeffReturnType;
  typedef typename PlainObject::PacketScalar PacketScalar;
  typedef typename PlainObject::PacketReturnType PacketReturnType;

  // All other functions are forwarded to m_resultImpl

  CoeffReturnType coeff(Index row, Index col) const 
  { 
    return m_resultImpl.coeff(row, col); 
  }
  
  CoeffReturnType coeff(Index index) const 
  { 
    return m_resultImpl.coeff(index); 
  }
  
  Scalar& coeffRef(Index row, Index col) 
  { 
    return m_resultImpl.coeffRef(row, col); 
  }
  
  Scalar& coeffRef(Index index) 
  { 
    return m_resultImpl.coeffRef(index); 
  }

  template<int LoadMode> 
  PacketReturnType packet(Index row, Index col) const
  {
    return m_resultImpl.template packet<LoadMode>(row, col);
  }

  template<int LoadMode> 
  PacketReturnType packet(Index index) const
  {
    return m_resultImpl.packet<LoadMode>(index);
  }

  template<int StoreMode> 
  void writePacket(Index row, Index col, const PacketScalar& x)
  {
    m_resultImpl.template writePacket<StoreMode>(row, col, x);
  }

  template<int StoreMode> 
  void writePacket(Index index, const PacketScalar& x)
  {
    m_resultImpl.template writePacket<StoreMode>(index, x);
  }

protected:
  PlainObject m_result;
  typename evaluator<PlainObject>::nestedType m_resultImpl;
};

// -------------------- Transpose --------------------

template<typename ArgType>
struct evaluator_impl<Transpose<ArgType> >
  : evaluator_impl_base<Transpose<ArgType> >
{
  typedef Transpose<ArgType> XprType;

  evaluator_impl(const XprType& t) : m_argImpl(t.nestedExpression()) {}

  typedef typename XprType::Index Index;
  typedef typename XprType::Scalar Scalar;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketScalar PacketScalar;
  typedef typename XprType::PacketReturnType PacketReturnType;

  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_argImpl.coeff(col, row);
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_argImpl.coeff(index);
  }

  Scalar& coeffRef(Index row, Index col)
  {
    return m_argImpl.coeffRef(col, row);
  }

  typename XprType::Scalar& coeffRef(Index index)
  {
    return m_argImpl.coeffRef(index);
  }

  template<int LoadMode>
  PacketReturnType packet(Index row, Index col) const
  {
    return m_argImpl.template packet<LoadMode>(col, row);
  }

  template<int LoadMode>
  PacketReturnType packet(Index index) const
  {
    return m_argImpl.template packet<LoadMode>(index);
  }

  template<int StoreMode> 
  void writePacket(Index row, Index col, const PacketScalar& x)
  {
    m_argImpl.template writePacket<StoreMode>(col, row, x);
  }

  template<int StoreMode> 
  void writePacket(Index index, const PacketScalar& x)
  {
    m_argImpl.template writePacket<StoreMode>(index, x);
  }

protected:
  typename evaluator<ArgType>::nestedType m_argImpl;
};

// -------------------- CwiseNullaryOp --------------------

template<typename NullaryOp, typename PlainObjectType>
struct evaluator_impl<CwiseNullaryOp<NullaryOp,PlainObjectType> >
{
  typedef CwiseNullaryOp<NullaryOp,PlainObjectType> XprType;

  evaluator_impl(const XprType& n) 
    : m_functor(n.functor()) 
  { }

  typedef typename XprType::Index Index;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketScalar PacketScalar;

  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_functor(row, col);
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_functor(index);
  }

  template<int LoadMode>
  PacketScalar packet(Index row, Index col) const
  {
    return m_functor.packetOp(row, col);
  }

  template<int LoadMode>
  PacketScalar packet(Index index) const
  {
    return m_functor.packetOp(index);
  }

protected:
  const NullaryOp m_functor;
};

// -------------------- CwiseUnaryOp --------------------

template<typename UnaryOp, typename ArgType>
struct evaluator_impl<CwiseUnaryOp<UnaryOp, ArgType> >
{
  typedef CwiseUnaryOp<UnaryOp, ArgType> XprType;

  evaluator_impl(const XprType& op) 
    : m_functor(op.functor()), 
      m_argImpl(op.nestedExpression()) 
  { }

  typedef typename XprType::Index Index;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketScalar PacketScalar;

  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_functor(m_argImpl.coeff(row, col));
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_functor(m_argImpl.coeff(index));
  }

  template<int LoadMode>
  PacketScalar packet(Index row, Index col) const
  {
    return m_functor.packetOp(m_argImpl.template packet<LoadMode>(row, col));
  }

  template<int LoadMode>
  PacketScalar packet(Index index) const
  {
    return m_functor.packetOp(m_argImpl.template packet<LoadMode>(index));
  }

protected:
  const UnaryOp m_functor;
  typename evaluator<ArgType>::nestedType m_argImpl;
};

// -------------------- CwiseBinaryOp --------------------

template<typename BinaryOp, typename Lhs, typename Rhs>
struct evaluator_impl<CwiseBinaryOp<BinaryOp, Lhs, Rhs> >
{
  typedef CwiseBinaryOp<BinaryOp, Lhs, Rhs> XprType;

  evaluator_impl(const XprType& xpr) 
    : m_functor(xpr.functor()),
      m_lhsImpl(xpr.lhs()), 
      m_rhsImpl(xpr.rhs())  
  { }

  typedef typename XprType::Index Index;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketScalar PacketScalar;

  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_functor(m_lhsImpl.coeff(row, col), m_rhsImpl.coeff(row, col));
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_functor(m_lhsImpl.coeff(index), m_rhsImpl.coeff(index));
  }

  template<int LoadMode>
  PacketScalar packet(Index row, Index col) const
  {
    return m_functor.packetOp(m_lhsImpl.template packet<LoadMode>(row, col),
			      m_rhsImpl.template packet<LoadMode>(row, col));
  }

  template<int LoadMode>
  PacketScalar packet(Index index) const
  {
    return m_functor.packetOp(m_lhsImpl.template packet<LoadMode>(index),
			      m_rhsImpl.template packet<LoadMode>(index));
  }

protected:
  const BinaryOp m_functor;
  typename evaluator<Lhs>::nestedType m_lhsImpl;
  typename evaluator<Rhs>::nestedType m_rhsImpl;
};

// -------------------- CwiseTernaryOp --------------------

template<typename TernaryOp, typename Arg1, typename Arg2, typename Arg3>
struct evaluator_impl<CwiseTernaryOp<TernaryOp, Arg1, Arg2, Arg3> >
{
  typedef CwiseTernaryOp<TernaryOp, Arg1, Arg2, Arg3> XprType;

  evaluator_impl(const XprType& xpr)
    : m_functor(xpr.functor()),
      m_arg1Impl(xpr.arg1()),
      m_arg2Impl(xpr.arg2()),
      m_arg3Impl(xpr.arg3())
  { }

  typedef typename XprType::Index Index;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketScalar PacketScalar;

  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_functor(m_arg1Impl.coeff(row, col),
                     m_arg2Impl.coeff(row, col),
                     m_arg3Impl.coeff(row, col));
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_functor(m_arg1Impl.coeff(index),
                     m_arg2Impl.coeff(index),
                     m_arg3Impl.coeff(index));
  }

  template<int LoadMode>
  PacketScalar packet(Index row, Index col) const
  {
    return m_functor.packetOp(m_arg1Impl.template packet<LoadMode>(row, col),
                              m_arg2Impl.template packet<LoadMode>(row, col),
                              m_arg3Impl.template packet<LoadMode>(row, col));
  }

  template<int LoadMode>
  PacketScalar packet(Index index) const
  {
    return m_functor.packetOp(m_arg1Impl.template packet<LoadMode>(index),
                              m_arg2Impl.template packet<LoadMode>(index),
                              m_arg3Impl.template packet<LoadMode>(index));
  }

protected:
  const TernaryOp m_functor;
  typename evaluator<Arg1>::nestedType m_arg1Impl;
  typename evaluator<Arg2>::nestedType m_arg2Impl;
  typename evaluator<Arg3>::nestedType m_arg3Impl;
};


// -------------------- CwiseUnaryView --------------------

template<typename UnaryOp, typename ArgType>
struct evaluator_impl<CwiseUnaryView<UnaryOp, ArgType> >
  : evaluator_impl_base<CwiseUnaryView<UnaryOp, ArgType> >
{
  typedef CwiseUnaryView<UnaryOp, ArgType> XprType;

  evaluator_impl(const XprType& op) 
    : m_unaryOp(op.functor()), 
      m_argImpl(op.nestedExpression()) 
  { }

  typedef typename XprType::Index Index;
  typedef typename XprType::Scalar Scalar;
  typedef typename XprType::CoeffReturnType CoeffReturnType;

  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_unaryOp(m_argImpl.coeff(row, col));
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_unaryOp(m_argImpl.coeff(index));
  }

  Scalar& coeffRef(Index row, Index col)
  {
    return m_unaryOp(m_argImpl.coeffRef(row, col));
  }

  Scalar& coeffRef(Index index)
  {
    return m_unaryOp(m_argImpl.coeffRef(index));
  }

protected:
  const UnaryOp m_unaryOp;
  typename evaluator<ArgType>::nestedType m_argImpl;
};

// -------------------- Map --------------------

template<typename Derived, int AccessorsType>
struct evaluator_impl<MapBase<Derived, AccessorsType> >
  : evaluator_impl_base<Derived>
{
  typedef MapBase<Derived, AccessorsType> MapType;
  typedef Derived XprType;

  typedef typename XprType::PointerType PointerType;
  typedef typename XprType::Index Index;
  typedef typename XprType::Scalar Scalar;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketScalar PacketScalar;
  typedef typename XprType::PacketReturnType PacketReturnType;
  
  evaluator_impl(const XprType& map) 
    : m_data(const_cast<PointerType>(map.data())),  
      m_rowStride(map.rowStride()),
      m_colStride(map.colStride())
  { }
 
  enum {
    RowsAtCompileTime = XprType::RowsAtCompileTime
  };
 
  CoeffReturnType coeff(Index row, Index col) const 
  { 
    return m_data[col * m_colStride + row * m_rowStride];
  }
  
  CoeffReturnType coeff(Index index) const 
  { 
    return coeff(RowsAtCompileTime == 1 ? 0 : index,
		 RowsAtCompileTime == 1 ? index : 0);
  }

  Scalar& coeffRef(Index row, Index col) 
  { 
    return m_data[col * m_colStride + row * m_rowStride];
  }
  
  Scalar& coeffRef(Index index) 
  { 
    return coeffRef(RowsAtCompileTime == 1 ? 0 : index,
		    RowsAtCompileTime == 1 ? index : 0);
  }
 
  template<int LoadMode> 
  PacketReturnType packet(Index row, Index col) const 
  { 
    PointerType ptr = m_data + row * m_rowStride + col * m_colStride;
    return internal::ploadt<PacketScalar, LoadMode>(ptr);
  }

  template<int LoadMode> 
  PacketReturnType packet(Index index) const 
  { 
    return packet<LoadMode>(RowsAtCompileTime == 1 ? 0 : index,
			    RowsAtCompileTime == 1 ? index : 0);
  }
  
  template<int StoreMode> 
  void writePacket(Index row, Index col, const PacketScalar& x) 
  { 
    PointerType ptr = m_data + row * m_rowStride + col * m_colStride;
    return internal::pstoret<Scalar, PacketScalar, StoreMode>(ptr, x);
  }
  
  template<int StoreMode> 
  void writePacket(Index index, const PacketScalar& x) 
  { 
    return writePacket<StoreMode>(RowsAtCompileTime == 1 ? 0 : index,
				  RowsAtCompileTime == 1 ? index : 0,
				  x);
  }
 
protected:
  PointerType m_data;
  int m_rowStride;
  int m_colStride;
};

template<typename PlainObjectType, int MapOptions, typename StrideType> 
struct evaluator_impl<Map<PlainObjectType, MapOptions, StrideType> >
  : public evaluator_impl<MapBase<Map<PlainObjectType, MapOptions, StrideType> > >
{
  typedef Map<PlainObjectType, MapOptions, StrideType> XprType;

  evaluator_impl(const XprType& map) 
    : evaluator_impl<MapBase<XprType> >(map) 
  { }
};

// -------------------- Block --------------------

template<typename ArgType, int BlockRows, int BlockCols, bool InnerPanel,
         bool HasDirectAccess = internal::has_direct_access<ArgType>::ret> struct block_evaluator;
         
template<typename ArgType, int BlockRows, int BlockCols, bool InnerPanel> 
struct evaluator_impl<Block<ArgType, BlockRows, BlockCols, InnerPanel> >
  : block_evaluator<ArgType, BlockRows, BlockCols, InnerPanel>
{
  typedef Block<ArgType, BlockRows, BlockCols, InnerPanel> XprType;
  typedef block_evaluator<ArgType, BlockRows, BlockCols, InnerPanel> block_evaluator_type;
  evaluator_impl(const XprType& block) : block_evaluator_type(block) {}
};

template<typename ArgType, int BlockRows, int BlockCols, bool InnerPanel>
struct block_evaluator<ArgType, BlockRows, BlockCols, InnerPanel, /*HasDirectAccess*/ false>
  : evaluator_impl_base<Block<ArgType, BlockRows, BlockCols, InnerPanel> >
{
  typedef Block<ArgType, BlockRows, BlockCols, InnerPanel> XprType;

  block_evaluator(const XprType& block) 
    : m_argImpl(block.nestedExpression()), 
      m_startRow(block.startRow()), 
      m_startCol(block.startCol()) 
  { }
 
  typedef typename XprType::Index Index;
  typedef typename XprType::Scalar Scalar;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketScalar PacketScalar;
  typedef typename XprType::PacketReturnType PacketReturnType;

  enum {
    RowsAtCompileTime = XprType::RowsAtCompileTime
  };
 
  CoeffReturnType coeff(Index row, Index col) const 
  { 
    return m_argImpl.coeff(m_startRow.value() + row, m_startCol.value() + col); 
  }
  
  CoeffReturnType coeff(Index index) const 
  { 
    return coeff(RowsAtCompileTime == 1 ? 0 : index,
		 RowsAtCompileTime == 1 ? index : 0);
  }

  Scalar& coeffRef(Index row, Index col) 
  { 
    return m_argImpl.coeffRef(m_startRow.value() + row, m_startCol.value() + col); 
  }
  
  Scalar& coeffRef(Index index) 
  { 
    return coeffRef(RowsAtCompileTime == 1 ? 0 : index,
		    RowsAtCompileTime == 1 ? index : 0);
  }
 
  template<int LoadMode> 
  PacketReturnType packet(Index row, Index col) const 
  { 
    return m_argImpl.template packet<LoadMode>(m_startRow.value() + row, m_startCol.value() + col); 
  }

  template<int LoadMode> 
  PacketReturnType packet(Index index) const 
  { 
    return packet<LoadMode>(RowsAtCompileTime == 1 ? 0 : index,
			    RowsAtCompileTime == 1 ? index : 0);
  }
  
  template<int StoreMode> 
  void writePacket(Index row, Index col, const PacketScalar& x) 
  { 
    return m_argImpl.template writePacket<StoreMode>(m_startRow.value() + row, m_startCol.value() + col, x); 
  }
  
  template<int StoreMode> 
  void writePacket(Index index, const PacketScalar& x) 
  { 
    return writePacket<StoreMode>(RowsAtCompileTime == 1 ? 0 : index,
				  RowsAtCompileTime == 1 ? index : 0,
				  x);
  }
 
protected:
  typename evaluator<ArgType>::nestedType m_argImpl;
  const variable_if_dynamic<Index, ArgType::RowsAtCompileTime == 1 ? 0 : Dynamic> m_startRow;
  const variable_if_dynamic<Index, ArgType::ColsAtCompileTime == 1 ? 0 : Dynamic> m_startCol;
};

// TODO: This evaluator does not actually use the child evaluator; 
// all action is via the data() as returned by the Block expression.

template<typename ArgType, int BlockRows, int BlockCols, bool InnerPanel> 
struct block_evaluator<ArgType, BlockRows, BlockCols, InnerPanel, /* HasDirectAccess */ true>
  : evaluator_impl<MapBase<Block<ArgType, BlockRows, BlockCols, InnerPanel> > >
{
  typedef Block<ArgType, BlockRows, BlockCols, InnerPanel> XprType;

  block_evaluator(const XprType& block) 
    : evaluator_impl<MapBase<XprType> >(block) 
  { }
};


// -------------------- Select --------------------

template<typename ConditionMatrixType, typename ThenMatrixType, typename ElseMatrixType>
struct evaluator_impl<Select<ConditionMatrixType, ThenMatrixType, ElseMatrixType> >
{
  typedef Select<ConditionMatrixType, ThenMatrixType, ElseMatrixType> XprType;

  evaluator_impl(const XprType& select) 
    : m_conditionImpl(select.conditionMatrix()),
      m_thenImpl(select.thenMatrix()),
      m_elseImpl(select.elseMatrix())
  { }
 
  typedef typename XprType::Index Index;
  typedef typename XprType::CoeffReturnType CoeffReturnType;

  CoeffReturnType coeff(Index row, Index col) const
  {
    if (m_conditionImpl.coeff(row, col))
      return m_thenImpl.coeff(row, col);
    else
      return m_elseImpl.coeff(row, col);
  }

  CoeffReturnType coeff(Index index) const
  {
    if (m_conditionImpl.coeff(index))
      return m_thenImpl.coeff(index);
    else
      return m_elseImpl.coeff(index);
  }
 
protected:
  typename evaluator<ConditionMatrixType>::nestedType m_conditionImpl;
  typename evaluator<ThenMatrixType>::nestedType m_thenImpl;
  typename evaluator<ElseMatrixType>::nestedType m_elseImpl;
};


// -------------------- Replicate --------------------

template<typename ArgType, int RowFactor, int ColFactor> 
struct evaluator_impl<Replicate<ArgType, RowFactor, ColFactor> >
{
  typedef Replicate<ArgType, RowFactor, ColFactor> XprType;

  evaluator_impl(const XprType& replicate) 
    : m_argImpl(replicate.nestedExpression()),
      m_rows(replicate.nestedExpression().rows()),
      m_cols(replicate.nestedExpression().cols())
  { }
 
  typedef typename XprType::Index Index;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketReturnType PacketReturnType;

  CoeffReturnType coeff(Index row, Index col) const
  {
    // try to avoid using modulo; this is a pure optimization strategy
    const Index actual_row = internal::traits<XprType>::RowsAtCompileTime==1 ? 0
                           : RowFactor==1 ? row
                           : row % m_rows.value();
    const Index actual_col = internal::traits<XprType>::ColsAtCompileTime==1 ? 0
                           : ColFactor==1 ? col
                           : col % m_cols.value();
    
    return m_argImpl.coeff(actual_row, actual_col);
  }

  template<int LoadMode>
  PacketReturnType packet(Index row, Index col) const
  {
    const Index actual_row = internal::traits<XprType>::RowsAtCompileTime==1 ? 0
                           : RowFactor==1 ? row
                           : row % m_rows.value();
    const Index actual_col = internal::traits<XprType>::ColsAtCompileTime==1 ? 0
                           : ColFactor==1 ? col
                           : col % m_cols.value();

    return m_argImpl.template packet<LoadMode>(actual_row, actual_col);
  }
 
protected:
  typename evaluator<ArgType>::nestedType m_argImpl;
  const variable_if_dynamic<Index, XprType::RowsAtCompileTime> m_rows;
  const variable_if_dynamic<Index, XprType::ColsAtCompileTime> m_cols;
};


// -------------------- PartialReduxExpr --------------------
//
// This is a wrapper around the expression object. 
// TODO: Find out how to write a proper evaluator without duplicating
//       the row() and col() member functions.

template< typename ArgType, typename MemberOp, int Direction>
struct evaluator_impl<PartialReduxExpr<ArgType, MemberOp, Direction> >
{
  typedef PartialReduxExpr<ArgType, MemberOp, Direction> XprType;

  evaluator_impl(const XprType expr)
    : m_expr(expr)
  { }

  typedef typename XprType::Index Index;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
 
  CoeffReturnType coeff(Index row, Index col) const 
  { 
    return m_expr.coeff(row, col);
  }
  
  CoeffReturnType coeff(Index index) const 
  { 
    return m_expr.coeff(index);
  }

protected:
  const XprType m_expr;
};


// -------------------- MatrixWrapper and ArrayWrapper --------------------
//
// evaluator_impl_wrapper_base<T> is a common base class for the
// MatrixWrapper and ArrayWrapper evaluators.

template<typename XprType>
struct evaluator_impl_wrapper_base
  : evaluator_impl_base<XprType>
{
  typedef typename remove_all<typename XprType::NestedExpressionType>::type ArgType;

  evaluator_impl_wrapper_base(const ArgType& arg) : m_argImpl(arg) {}

  typedef typename ArgType::Index Index;
  typedef typename ArgType::Scalar Scalar;
  typedef typename ArgType::CoeffReturnType CoeffReturnType;
  typedef typename ArgType::PacketScalar PacketScalar;
  typedef typename ArgType::PacketReturnType PacketReturnType;

  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_argImpl.coeff(row, col);
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_argImpl.coeff(index);
  }

  Scalar& coeffRef(Index row, Index col)
  {
    return m_argImpl.coeffRef(row, col);
  }

  Scalar& coeffRef(Index index)
  {
    return m_argImpl.coeffRef(index);
  }

  template<int LoadMode> 
  PacketReturnType packet(Index row, Index col) const
  {
    return m_argImpl.template packet<LoadMode>(row, col);
  }

  template<int LoadMode> 
  PacketReturnType packet(Index index) const
  {
    return m_argImpl.template packet<LoadMode>(index);
  }

  template<int StoreMode> 
  void writePacket(Index row, Index col, const PacketScalar& x)
  {
    m_argImpl.template writePacket<StoreMode>(row, col, x);
  }

  template<int StoreMode> 
  void writePacket(Index index, const PacketScalar& x)
  {
    m_argImpl.template writePacket<StoreMode>(index, x);
  }

protected:
  typename evaluator<ArgType>::nestedType m_argImpl;
};

template<typename TArgType>
struct evaluator_impl<MatrixWrapper<TArgType> >
  : evaluator_impl_wrapper_base<MatrixWrapper<TArgType> >
{
  typedef MatrixWrapper<TArgType> XprType;

  evaluator_impl(const XprType& wrapper) 
    : evaluator_impl_wrapper_base<MatrixWrapper<TArgType> >(wrapper.nestedExpression())
  { }
};

template<typename TArgType>
struct evaluator_impl<ArrayWrapper<TArgType> >
  : evaluator_impl_wrapper_base<ArrayWrapper<TArgType> >
{
  typedef ArrayWrapper<TArgType> XprType;

  evaluator_impl(const XprType& wrapper) 
    : evaluator_impl_wrapper_base<ArrayWrapper<TArgType> >(wrapper.nestedExpression())
  { }
};


// -------------------- Reverse --------------------

// defined in Reverse.h:
template<typename PacketScalar, bool ReversePacket> struct reverse_packet_cond;

template<typename ArgType, int Direction>
struct evaluator_impl<Reverse<ArgType, Direction> >
  : evaluator_impl_base<Reverse<ArgType, Direction> >
{
  typedef Reverse<ArgType, Direction> XprType;
  typedef typename XprType::Index Index;
  typedef typename XprType::Scalar Scalar;
  typedef typename XprType::CoeffReturnType CoeffReturnType;
  typedef typename XprType::PacketScalar PacketScalar;
  typedef typename XprType::PacketReturnType PacketReturnType;

  enum {
    PacketSize = internal::packet_traits<Scalar>::size,
    IsRowMajor = XprType::IsRowMajor,
    IsColMajor = !IsRowMajor,
    ReverseRow = (Direction == Vertical)   || (Direction == BothDirections),
    ReverseCol = (Direction == Horizontal) || (Direction == BothDirections),
    OffsetRow  = ReverseRow && IsColMajor ? PacketSize : 1,
    OffsetCol  = ReverseCol && IsRowMajor ? PacketSize : 1,
    ReversePacket = (Direction == BothDirections)
                    || ((Direction == Vertical)   && IsColMajor)
                    || ((Direction == Horizontal) && IsRowMajor)
  };
  typedef internal::reverse_packet_cond<PacketScalar,ReversePacket> reverse_packet;

  evaluator_impl(const XprType& reverse) 
    : m_argImpl(reverse.nestedExpression()),
      m_rows(ReverseRow ? reverse.nestedExpression().rows() : 0),
      m_cols(ReverseCol ? reverse.nestedExpression().cols() : 0)
  { }
 
  CoeffReturnType coeff(Index row, Index col) const
  {
    return m_argImpl.coeff(ReverseRow ? m_rows.value() - row - 1 : row,
			   ReverseCol ? m_cols.value() - col - 1 : col);
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_argImpl.coeff(m_rows.value() * m_cols.value() - index - 1);
  }

  Scalar& coeffRef(Index row, Index col)
  {
    return m_argImpl.coeffRef(ReverseRow ? m_rows.value() - row - 1 : row,
			      ReverseCol ? m_cols.value() - col - 1 : col);
  }

  Scalar& coeffRef(Index index)
  {
    return m_argImpl.coeffRef(m_rows.value() * m_cols.value() - index - 1);
  }

  template<int LoadMode>
  PacketScalar packet(Index row, Index col) const
  {
    return reverse_packet::run(m_argImpl.template packet<LoadMode>(
                                  ReverseRow ? m_rows.value() - row - OffsetRow : row,
                                  ReverseCol ? m_cols.value() - col - OffsetCol : col));
  }

  template<int LoadMode>
  PacketScalar packet(Index index) const
  {
    return preverse(m_argImpl.template packet<LoadMode>(m_rows.value() * m_cols.value() - index - PacketSize));
  }

  template<int LoadMode>
  void writePacket(Index row, Index col, const PacketScalar& x)
  {
    m_argImpl.template writePacket<LoadMode>(
                                  ReverseRow ? m_rows.value() - row - OffsetRow : row,
                                  ReverseCol ? m_cols.value() - col - OffsetCol : col,
                                  reverse_packet::run(x));
  }

  template<int LoadMode>
  void writePacket(Index index, const PacketScalar& x)
  {
    m_argImpl.template writePacket<LoadMode>
      (m_rows.value() * m_cols.value() - index - PacketSize, preverse(x));
  }
 
protected:
  typename evaluator<ArgType>::nestedType m_argImpl;

  // If we do not reverse rows, then we do not need to know the number of rows; same for columns
  const variable_if_dynamic<Index, ReverseRow ? ArgType::RowsAtCompileTime : 0> m_rows;
  const variable_if_dynamic<Index, ReverseCol ? ArgType::ColsAtCompileTime : 0> m_cols;
};


// -------------------- Diagonal --------------------

template<typename ArgType, int DiagIndex>
struct evaluator_impl<Diagonal<ArgType, DiagIndex> >
  : evaluator_impl_base<Diagonal<ArgType, DiagIndex> >
{
  typedef Diagonal<ArgType, DiagIndex> XprType;

  evaluator_impl(const XprType& diagonal) 
    : m_argImpl(diagonal.nestedExpression()),
      m_index(diagonal.index())
  { }
 
  typedef typename XprType::Index Index;
  typedef typename XprType::Scalar Scalar;
  typedef typename XprType::CoeffReturnType CoeffReturnType;

  CoeffReturnType coeff(Index row, Index) const
  {
    return m_argImpl.coeff(row + rowOffset(), row + colOffset());
  }

  CoeffReturnType coeff(Index index) const
  {
    return m_argImpl.coeff(index + rowOffset(), index + colOffset());
  }

  Scalar& coeffRef(Index row, Index)
  {
    return m_argImpl.coeffRef(row + rowOffset(), row + colOffset());
  }

  Scalar& coeffRef(Index index)
  {
    return m_argImpl.coeffRef(index + rowOffset(), index + colOffset());
  }

protected:
  typename evaluator<ArgType>::nestedType m_argImpl;
  const internal::variable_if_dynamicindex<Index, XprType::DiagIndex> m_index;

private:
  EIGEN_STRONG_INLINE Index rowOffset() const { return m_index.value() > 0 ? 0 : -m_index.value(); }
  EIGEN_STRONG_INLINE Index colOffset() const { return m_index.value() > 0 ? m_index.value() : 0; }
};

} // namespace internal

} // end namespace Eigen

#endif // EIGEN_COREEVALUATORS_H