* resurected Flagged from Eigen2Support

* reimplement .diagonal() for ProductBase to make (A*B).diagonal() more efficient!

Eigen/src/Eigen2Support/Lazy.h

@@ -0,0 +1,82 @@
+// This file is part of Eigen, a lightweight C++ template library
+// for linear algebra.
+//
+// Copyright (C) 2008 Benoit Jacob <jacob.benoit.1@gmail.com>
+//
+// 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_LAZY_H
+#define EIGEN_LAZY_H
+
+/** \deprecated it is only used by lazy() which is deprecated
+  *
+  * \returns an expression of *this with added flags
+  *
+  * Example: \include MatrixBase_marked.cpp
+  * Output: \verbinclude MatrixBase_marked.out
+  *
+  * \sa class Flagged, extract(), part()
+  */
+template<typename Derived>
+template<unsigned int Added>
+inline const Flagged<Derived, Added, 0>
+MatrixBase<Derived>::marked() const
+{
+  return derived();
+}
+
+/** \deprecated use MatrixBase::noalias()
+  *
+  * \returns an expression of *this with the EvalBeforeAssigningBit flag removed.
+  *
+  * Example: \include MatrixBase_lazy.cpp
+  * Output: \verbinclude MatrixBase_lazy.out
+  *
+  * \sa class Flagged, marked()
+  */
+template<typename Derived>
+inline const Flagged<Derived, 0, EvalBeforeAssigningBit>
+MatrixBase<Derived>::lazy() const
+{
+  return derived();
+}
+
+
+/** \internal
+  * Overloaded to perform an efficient C += (A*B).lazy() */
+template<typename Derived>
+template<typename ProductDerived, typename Lhs, typename Rhs>
+Derived& MatrixBase<Derived>::operator+=(const Flagged<ProductBase<ProductDerived, Lhs,Rhs>, 0,
+                                                       EvalBeforeAssigningBit>& other)
+{
+  other._expression().derived().addTo(derived()); return derived();
+}
+
+/** \internal
+  * Overloaded to perform an efficient C -= (A*B).lazy() */
+template<typename Derived>
+template<typename ProductDerived, typename Lhs, typename Rhs>
+Derived& MatrixBase<Derived>::operator-=(const Flagged<ProductBase<ProductDerived, Lhs,Rhs>, 0,
+                                                       EvalBeforeAssigningBit>& other)
+{
+  other._expression().derived().subTo(derived()); return derived();
+}
+
+#endif // EIGEN_LAZY_H