introduce a new LvalueBit flag and split DenseCoeffBase into three level of accessors

Eigen/src/Core/BandMatrix.h

@@ -55,7 +55,7 @@ struct ei_traits<BandMatrix<_Scalar,Rows,Cols,Supers,Subs,Options> >
     ColsAtCompileTime = Cols,
     MaxRowsAtCompileTime = Rows,
     MaxColsAtCompileTime = Cols,
-    Flags = 0
+    Flags = LvalueBit
   };
 };
 

Eigen/src/Core/Block.h

@@ -93,7 +93,7 @@ struct ei_traits<Block<XprType, BlockRows, BlockCols, HasDirectAccess> > : ei_tr
                        && (InnerStrideAtCompileTime == 1)
                         ? PacketAccessBit : 0,
     FlagsLinearAccessBit = (RowsAtCompileTime == 1 || ColsAtCompileTime == 1) ? LinearAccessBit : 0,
-    Flags0 = ei_traits<XprType>::Flags & (HereditaryBits | MaskPacketAccessBit | DirectAccessBit),
+    Flags0 = ei_traits<XprType>::Flags & (HereditaryBits | MaskPacketAccessBit | LvalueBit | DirectAccessBit),
     Flags1 = Flags0 | FlagsLinearAccessBit,
     Flags = (Flags1 & ~RowMajorBit) | (IsRowMajor ? RowMajorBit : 0)
   };

Eigen/src/Core/CwiseUnaryView.h

@@ -48,7 +48,7 @@ struct ei_traits<CwiseUnaryView<ViewOp, MatrixType> >
   typedef typename MatrixType::Nested MatrixTypeNested;
   typedef typename ei_cleantype<MatrixTypeNested>::type _MatrixTypeNested;
   enum {
-    Flags = (ei_traits<_MatrixTypeNested>::Flags & (HereditaryBits | LinearAccessBit | DirectAccessBit)),
+    Flags = (ei_traits<_MatrixTypeNested>::Flags & (HereditaryBits | LvalueBit | LinearAccessBit | DirectAccessBit)),
     CoeffReadCost = ei_traits<_MatrixTypeNested>::CoeffReadCost + ei_functor_traits<ViewOp>::Cost,
     MatrixTypeInnerStride =  ei_inner_stride_at_compile_time<MatrixType>::ret,
     // need to cast the sizeof's from size_t to int explicitly, otherwise:

Eigen/src/Core/DenseCoeffsBase.h

@@ -25,15 +25,15 @@
 #ifndef EIGEN_DENSECOEFFSBASE_H
 #define EIGEN_DENSECOEFFSBASE_H
 
-template<typename Derived, bool EnableDirectAccessAPI>
-class DenseCoeffsBase : public EigenBase<Derived>
+template<typename Derived>
+class DenseCoeffsBase<Derived,ReadOnlyAccessors> : public EigenBase<Derived>
 {
   public:
     typedef typename ei_traits<Derived>::StorageKind StorageKind;
     typedef typename ei_traits<Derived>::Index Index;
     typedef typename ei_traits<Derived>::Scalar Scalar;
     typedef typename ei_packet_traits<Scalar>::type PacketScalar;
-    typedef typename ei_meta_if<ei_has_direct_access<Derived>::ret,
+    typedef typename ei_meta_if<bool(ei_traits<Derived>::Flags&LvalueBit),
                                 const Scalar&,
                                 typename ei_meta_if<ei_is_arithmetic<Scalar>::ret, Scalar, const Scalar>::ret
                                >::ret CoeffReturnType;
@@ -239,11 +239,11 @@ class DenseCoeffsBase : public EigenBase<Derived>
 };
 
 template<typename Derived>
-class DenseCoeffsBase<Derived, true> : public DenseCoeffsBase<Derived, false>
+class DenseCoeffsBase<Derived, WriteAccessors> : public DenseCoeffsBase<Derived, ReadOnlyAccessors>
 {
   public:
 
-    typedef DenseCoeffsBase<Derived, false> Base;
+    typedef DenseCoeffsBase<Derived, ReadOnlyAccessors> Base;
 
     typedef typename ei_traits<Derived>::StorageKind StorageKind;
     typedef typename ei_traits<Derived>::Index Index;
@@ -512,6 +512,23 @@ class DenseCoeffsBase<Derived, true> : public DenseCoeffsBase<Derived, false>
     }
 #endif
 
+};
+
+template<typename Derived>
+class DenseCoeffsBase<Derived, DirectAccessors> : public DenseCoeffsBase<Derived, WriteAccessors>
+{
+  public:
+
+    typedef DenseCoeffsBase<Derived, WriteAccessors> Base;
+    typedef typename ei_traits<Derived>::Index Index;
+    typedef typename ei_traits<Derived>::Scalar Scalar;
+    typedef typename NumTraits<Scalar>::Real RealScalar;
+
+    using Base::rows;
+    using Base::cols;
+    using Base::size;
+    using Base::derived;
+
     /** \returns the pointer increment between two consecutive elements within a slice in the inner direction.
       *
       * \sa outerStride(), rowStride(), colStride()
@@ -531,6 +548,7 @@ class DenseCoeffsBase<Derived, true> : public DenseCoeffsBase<Derived, false>
       return derived().outerStride();
     }
 
+    // FIXME shall we remove it ?
     inline Index stride() const
     {
       return Derived::IsVectorAtCompileTime ? innerStride() : outerStride();

Eigen/src/Core/Diagonal.h

@@ -62,7 +62,7 @@ struct ei_traits<Diagonal<MatrixType,DiagIndex> >
                                                                     MatrixType::MaxColsAtCompileTime)
                          : (EIGEN_SIZE_MIN_PREFER_FIXED(MatrixType::MaxRowsAtCompileTime, MatrixType::MaxColsAtCompileTime) - AbsDiagIndex),
     MaxColsAtCompileTime = 1,
-    Flags = (unsigned int)_MatrixTypeNested::Flags & (HereditaryBits | LinearAccessBit | DirectAccessBit) & ~RowMajorBit,
+    Flags = (unsigned int)_MatrixTypeNested::Flags & (HereditaryBits | LinearAccessBit | LvalueBit | DirectAccessBit) & ~RowMajorBit,
     CoeffReadCost = _MatrixTypeNested::CoeffReadCost,
     MatrixTypeOuterStride = ei_outer_stride_at_compile_time<MatrixType>::ret,
     InnerStrideAtCompileTime = MatrixTypeOuterStride == Dynamic ? Dynamic : MatrixTypeOuterStride+1,

Eigen/src/Core/DiagonalMatrix.h

@@ -105,6 +105,9 @@ struct ei_traits<DiagonalMatrix<_Scalar,SizeAtCompileTime,MaxSizeAtCompileTime>
   typedef Matrix<_Scalar,SizeAtCompileTime,1,0,MaxSizeAtCompileTime,1> DiagonalVectorType;
   typedef Dense StorageKind;
   typedef DenseIndex Index;
+  enum {
+    Flags = LvalueBit
+  };
 };
 
 template<typename _Scalar, int SizeAtCompileTime, int MaxSizeAtCompileTime>
@@ -213,7 +216,7 @@ struct ei_traits<DiagonalWrapper<_DiagonalVectorType> >
     ColsAtCompileTime = DiagonalVectorType::SizeAtCompileTime,
     MaxRowsAtCompileTime = DiagonalVectorType::SizeAtCompileTime,
     MaxColsAtCompileTime = DiagonalVectorType::SizeAtCompileTime,
-    Flags = 0
+    Flags =  ei_traits<DiagonalVectorType>::Flags & LvalueBit
   };
 };
 

Eigen/src/Core/Reverse.h

@@ -59,7 +59,7 @@ struct ei_traits<Reverse<MatrixType, Direction> >
     LinearAccess = ( (Direction==BothDirections) && (int(_MatrixTypeNested::Flags)&PacketAccessBit) )
                  ? LinearAccessBit : 0,
 
-    Flags = int(_MatrixTypeNested::Flags) & (HereditaryBits | PacketAccessBit | LinearAccess | DirectAccessBit),
+    Flags = int(_MatrixTypeNested::Flags) & (HereditaryBits | LvalueBit | PacketAccessBit | LinearAccess),
 
     CoeffReadCost = _MatrixTypeNested::CoeffReadCost
   };

Eigen/src/Core/util/Constants.h

@@ -139,6 +139,14 @@ const unsigned int DirectAccessBit = 0x20;
   * means the first coefficient packet is guaranteed to be aligned */
 const unsigned int AlignedBit = 0x40;
 
+/** \ingroup flags
+  *
+  * Means the expression is writable. Note that DirectAccessBit implies LvalueBit.
+  * Internaly, it is mainly used to enable the writable coeff accessors, and makes
+  * the read-only coeff accessors to return by const reference.
+  */
+const unsigned int LvalueBit = 0x80;
+
 const unsigned int NestByRefBit = 0x100;
 
 // list of flags that are inherited by default
@@ -234,6 +242,10 @@ enum {
   IsSparse
 };
 
+enum AccessorLevels {
+  ReadOnlyAccessors, WriteAccessors, DirectAccessors
+};
+
 enum DecompositionOptions {
   Pivoting            = 0x01, // LDLT,
   NoPivoting          = 0x02, // LDLT,

Eigen/src/Core/util/ForwardDeclarations.h

@@ -36,7 +36,10 @@ template<typename Derived> struct ei_has_direct_access
 
 template<typename Derived> struct EigenBase;
 template<typename Derived> class DenseBase;
-template<typename Derived, bool EnableDirectAccessAPI = ei_has_direct_access<Derived>::ret>
+template<typename Derived,
+         AccessorLevels Level = (ei_traits<Derived>::Flags & DirectAccessBit) ? DirectAccessors
+                              : (ei_traits<Derived>::Flags & LvalueBit) ? WriteAccessors
+                              : ReadOnlyAccessors>
 class DenseCoeffsBase;
 
 template<typename _Scalar, int _Rows, int _Cols,

Eigen/src/Core/util/XprHelper.h

@@ -155,7 +155,7 @@ class ei_compute_matrix_flags
     };
 
   public:
-    enum { ret = LinearAccessBit | DirectAccessBit | NestByRefBit | packet_access_bit | row_major_bit | aligned_bit };
+    enum { ret = LinearAccessBit | LvalueBit | DirectAccessBit | NestByRefBit | packet_access_bit | row_major_bit | aligned_bit };
 };
 
 template<int _Rows, int _Cols> struct ei_size_at_compile_time
@@ -355,7 +355,7 @@ template<typename T, int n=1, typename PlainObject = typename ei_eval<T>::type>
 
 template<unsigned int Flags> struct ei_are_flags_consistent
 {
-  enum { ret = true };
+  enum { ret = EIGEN_IMPLIES(bool(Flags&DirectAccessBit), bool(Flags&LvalueBit)) };
 };
 
 template<typename Derived, typename XprKind = typename ei_traits<Derived>::XprKind>

Eigen/src/Eigenvalues/HessenbergDecomposition.h

@@ -130,7 +130,7 @@ template<typename _MatrixType> class HessenbergDecomposition
     {
       if(matrix.rows()<2)
       {
-	m_isInitialized = true;
+        m_isInitialized = true;
         return;
       }
       m_hCoeffs.resize(matrix.rows()-1,1);
@@ -160,7 +160,7 @@ template<typename _MatrixType> class HessenbergDecomposition
       m_matrix = matrix;
       if(matrix.rows()<2)
       {
-	m_isInitialized = true;
+        m_isInitialized = true;
         return *this;
       }
       m_hCoeffs.resize(matrix.rows()-1,1);
@@ -360,7 +360,7 @@ template<typename MatrixType> struct HessenbergDecompositionMatrixHReturnType
       result = m_hess.packedMatrix();
       Index n = result.rows();
       if (n>2)
-	result.bottomLeftCorner(n-2, n-2).template triangularView<Lower>().setZero();
+        result.bottomLeftCorner(n-2, n-2).template triangularView<Lower>().setZero();
     }
 
     Index rows() const { return m_hess.packedMatrix().rows(); }

Eigen/src/Sparse/DynamicSparseMatrix.h

@@ -54,7 +54,7 @@ struct ei_traits<DynamicSparseMatrix<_Scalar, _Flags, _Index> >
     ColsAtCompileTime = Dynamic,
     MaxRowsAtCompileTime = Dynamic,
     MaxColsAtCompileTime = Dynamic,
-    Flags = _Flags | NestByRefBit,
+    Flags = _Flags | NestByRefBit | LvalueBit,
     CoeffReadCost = NumTraits<Scalar>::ReadCost,
     SupportedAccessPatterns = OuterRandomAccessPattern
   };

Eigen/src/Sparse/SparseMatrix.h

@@ -54,7 +54,7 @@ struct ei_traits<SparseMatrix<_Scalar, _Options, _Index> >
     ColsAtCompileTime = Dynamic,
     MaxRowsAtCompileTime = Dynamic,
     MaxColsAtCompileTime = Dynamic,
-    Flags = _Options | NestByRefBit,
+    Flags = _Options | NestByRefBit | LvalueBit,
     CoeffReadCost = NumTraits<Scalar>::ReadCost,
     SupportedAccessPatterns = InnerRandomAccessPattern
   };

Eigen/src/Sparse/SparseVector.h

@@ -48,7 +48,7 @@ struct ei_traits<SparseVector<_Scalar, _Options, _Index> >
     ColsAtCompileTime = IsColVector ? 1 : Dynamic,
     MaxRowsAtCompileTime = RowsAtCompileTime,
     MaxColsAtCompileTime = ColsAtCompileTime,
-    Flags = _Options | NestByRefBit,
+    Flags = _Options | NestByRefBit | LvalueBit,
     CoeffReadCost = NumTraits<Scalar>::ReadCost,
     SupportedAccessPatterns = InnerRandomAccessPattern
   };