Added ArrayBit to get the ability to manipulate a Matrix like a simple scalar.

In particular this flag changes the behavior of operator* to a coeff wise product.

Eigen/Core

@@ -27,6 +27,7 @@ namespace Eigen {
 
 #include "src/Core/Functors.h"
 #include "src/Core/MatrixBase.h"
+#include "src/Core/ArrayBase.h"
 #include "src/Core/Coeffs.h"
 #include "src/Core/Assign.h"
 #include "src/Core/MatrixStorage.h"

Eigen/src/Core/ArrayBase.h

@@ -0,0 +1,45 @@
+// 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_ARRAYBASE_H
+#define EIGEN_ARRAYBASE_H
+
+template<typename Derived> class ArrayBase<Derived,false> {};
+
+template<typename Derived> class ArrayBase<Derived,true>
+{
+    inline const Derived& derived() const { return *static_cast<const Derived*>(this); }
+    inline Derived& derived() { return *static_cast<Derived*>(this); }
+    inline Derived& const_cast_derived() const
+    { return *static_cast<Derived*>(const_cast<ArrayBase*>(this)); }
+public:
+    template<typename OtherDerived>
+    const Product<Derived,OtherDerived>
+    matrixProduct(const MatrixBase<OtherDerived> &other) const
+    {
+        return Product<Derived,OtherDerived>(derived(), other.derived());
+    }
+};
+
+#endif // EIGEN_ARRAYBASE_H

Eigen/src/Core/MatrixBase.h

@@ -49,7 +49,7 @@
   *
   * \nosubgrouping
   */
-template<typename Derived> class MatrixBase
+template<typename Derived> class MatrixBase : public ArrayBase<Derived>
 {
     struct CommaInitializer;
 
@@ -182,6 +182,24 @@ template<typename Derived> class MatrixBase
     };
     /** Represents a product scalar-matrix */
     typedef CwiseUnaryOp<ei_scalar_multiple_op<Scalar>, Derived> ScalarMultipleReturnType;
+    /** */
+    template<typename OtherDerived>
+    struct ProductReturnType
+    {
+      typedef typename ei_meta_if<
+            (Derived::Flags & OtherDerived::Flags & ArrayBit),
+            CwiseBinaryOp<ei_scalar_product_op<typename ei_traits<Derived>::Scalar>, Derived, OtherDerived>,
+            Product<Derived,OtherDerived>
+          >::ret Type;
+    };
+    /** the return type of MatrixBase::conjugate() */
+    typedef typename ei_meta_if<NumTraits<Scalar>::IsComplex,
+                        CwiseUnaryOp<ei_scalar_conjugate_op<Scalar>, Derived>,
+                        Derived&
+                     >::ret ConjugateReturnType;
+    /** the return type of MatrixBase::adjoint() */
+    typedef Transpose<NestByValue<typename ei_unref<ConjugateReturnType>::type> >
+            AdjointReturnType;
     //@}
 
     /// \name Copying and initialization
@@ -281,7 +299,7 @@ template<typename Derived> class MatrixBase
       */
     //@{
     template<typename OtherDerived>
-    const Product<Derived,OtherDerived>
+    const typename ProductReturnType<OtherDerived>::Type
     operator*(const MatrixBase<OtherDerived> &other) const;
 
     template<typename OtherDerived>
@@ -303,16 +321,6 @@ template<typename Derived> class MatrixBase
 
     Transpose<Derived> transpose();
     const Transpose<Derived> transpose() const;
-
-    /** the return type of MatrixBase::conjugate() */
-    typedef typename ei_meta_if<NumTraits<Scalar>::IsComplex,
-                        CwiseUnaryOp<ei_scalar_conjugate_op<Scalar>, Derived>,
-                        Derived&
-                     >::ret ConjugateReturnType;
-    /** the return type of MatrixBase::adjoint() */
-    typedef Transpose<
-                NestByValue<typename ei_unref<ConjugateReturnType>::type>
-              > AdjointReturnType;
     const AdjointReturnType adjoint() const;
     //@}
 

Eigen/src/Core/Product.h

@@ -320,10 +320,11 @@ template<typename Lhs, typename Rhs, int EvalMode> class Product : ei_no_assignm
   */
 template<typename Derived>
 template<typename OtherDerived>
-inline const Product<Derived,OtherDerived>
+inline const typename MatrixBase<Derived>::template ProductReturnType<OtherDerived>::Type
 MatrixBase<Derived>::operator*(const MatrixBase<OtherDerived> &other) const
 {
-  return Product<Derived,OtherDerived>(derived(), other.derived());
+  assert( (Derived::Flags&ArrayBit) == (OtherDerived::Flags) );
+  return typename ProductReturnType<OtherDerived>::Type(derived(), other.derived());
 }
 
 /** replaces \c *this by \c *this * \a other.

Eigen/src/Core/util/Constants.h

@@ -42,15 +42,17 @@ const unsigned int Like1DArrayBit = 0x20;   ///< means the expression can be see
 const unsigned int ZeroDiagBit = 0x40;      ///< means all diagonal coefficients are equal to 0
 const unsigned int UnitDiagBit = 0x80;      ///< means all diagonal coefficients are equal to 1
 const unsigned int SelfAdjointBit = 0x100;  ///< means the matrix is selfadjoint (M=M*).
-const unsigned int UpperTriangularBit = 0x200;    ///< means the strictly triangular lower part is 0
-const unsigned int LowerTriangularBit = 0x400;    ///< means the strictly triangular upper part is 0
-const unsigned int DirectAccessBit = 0x800; ///< means the underlying matrix data can be direclty accessed
+const unsigned int UpperTriangularBit = 0x200;  ///< means the strictly triangular lower part is 0
+const unsigned int LowerTriangularBit = 0x400;  ///< means the strictly triangular upper part is 0
+const unsigned int DirectAccessBit = 0x800;     ///< means the underlying matrix data can be direclty accessed
+const unsigned int ArrayBit = 0x1000;           ///< means the underlying matrix data can be direclty accessed
 
 // list of flags that are inherited by default
 const unsigned int HereditaryBits = RowMajorBit
                                   | EvalBeforeNestingBit
                                   | EvalBeforeAssigningBit
-                                  | LargeBit;
+                                  | LargeBit
+                                  | ArrayBit;
 
 // Possible values for the Mode parameter of part() and of extract()
 const unsigned int Upper = UpperTriangularBit;

Eigen/src/Core/util/ForwardDeclarations.h

@@ -50,6 +50,7 @@ template<typename MatrixType> class Map;
 template<int Direction, typename UnaryOp, typename MatrixType> class PartialRedux;
 template<typename MatrixType, unsigned int Mode> class Part;
 template<typename MatrixType, unsigned int Mode> class Extract;
+template<typename Derived, bool HasArrayFlag = int(ei_traits<Derived>::Flags) & ArrayBit> class ArrayBase;
 
 
 template<typename Scalar> struct ei_scalar_sum_op;

Eigen/src/Core/util/Meta.h

@@ -202,8 +202,8 @@ template<typename T, int n=1> struct ei_nested
     ei_must_nest_by_value<T>::ret,
     T,
     typename ei_meta_if<
-      int(ei_traits<T>::Flags) & EvalBeforeNestingBit
-      || (n+1) * int(NumTraits<typename ei_traits<T>::Scalar>::ReadCost) < (n-1) * int(T::CoeffReadCost),
+      (int(ei_traits<T>::Flags) & EvalBeforeNestingBit)
+      || ((n+1) * int(NumTraits<typename ei_traits<T>::Scalar>::ReadCost) < (n-1) * int(T::CoeffReadCost)),
       typename ei_eval<T>::type,
       const T&
     >::ret