From 13867c15cca7716ff36c2ee2c9b37ebe2721cd9a Mon Sep 17 00:00:00 2001
From: Benoit Jacob <jacob.benoit.1@gmail.com>
Date: Thu, 30 Dec 2010 07:47:51 -0500
Subject: [PATCH] fix compilation of code using e.g. Transpose<const
 Foo>::data() non-const-qualified. Same problem existed for coeffRef() and
 also in MapBase.h.

---
 Eigen/src/Core/MapBase.h   | 14 ++++++++++----
 Eigen/src/Core/Transpose.h | 13 ++++++++++---
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/Eigen/src/Core/MapBase.h b/Eigen/src/Core/MapBase.h
index d8ecdf2f4..826e4049d 100644
--- a/Eigen/src/Core/MapBase.h
+++ b/Eigen/src/Core/MapBase.h
@@ -201,15 +201,21 @@ template<typename Derived> class MapBase<Derived, WriteAccessors>
     using Base::rowStride;
     using Base::colStride;
 
-    inline const Scalar* data() const { return this->m_data; }
-    inline Scalar* data() { return this->m_data; } // no const-cast here so non-const-correct code will give a compile error
+    typedef typename internal::conditional<
+                    internal::is_lvalue<Derived>::value,
+                    Scalar,
+                    const Scalar
+                  >::type ScalarWithConstIfNotLvalue;
 
-    inline Scalar& coeffRef(Index row, Index col)
+    inline const Scalar* data() const { return this->m_data; }
+    inline ScalarWithConstIfNotLvalue* data() { return this->m_data; } // no const-cast here so non-const-correct code will give a compile error
+
+    inline ScalarWithConstIfNotLvalue& coeffRef(Index row, Index col)
     {
       return this->m_data[col * colStride() + row * rowStride()];
     }
 
-    inline Scalar& coeffRef(Index index)
+    inline ScalarWithConstIfNotLvalue& coeffRef(Index index)
     {
       EIGEN_STATIC_ASSERT_LINEAR_ACCESS(Derived)
       return this->m_data[index * innerStride()];
diff --git a/Eigen/src/Core/Transpose.h b/Eigen/src/Core/Transpose.h
index 1c9403eba..a5687790f 100644
--- a/Eigen/src/Core/Transpose.h
+++ b/Eigen/src/Core/Transpose.h
@@ -120,16 +120,23 @@ template<typename MatrixType> class TransposeImpl<MatrixType,Dense>
 
     inline Index innerStride() const { return derived().nestedExpression().innerStride(); }
     inline Index outerStride() const { return derived().nestedExpression().outerStride(); }
-    inline Scalar* data() { return derived().nestedExpression().data(); }
+
+    typedef typename internal::conditional<
+                       internal::is_lvalue<MatrixType>::value,
+                       Scalar,
+                       const Scalar
+                     >::type ScalarWithConstIfNotLvalue;
+
+    inline ScalarWithConstIfNotLvalue* data() { return derived().nestedExpression().data(); }
     inline const Scalar* data() const { return derived().nestedExpression().data(); }
 
-    inline Scalar& coeffRef(Index row, Index col)
+    inline ScalarWithConstIfNotLvalue& coeffRef(Index row, Index col)
     {
       EIGEN_STATIC_ASSERT_LVALUE(MatrixType)
       return derived().nestedExpression().const_cast_derived().coeffRef(col, row);
     }
 
-    inline Scalar& coeffRef(Index index)
+    inline ScalarWithConstIfNotLvalue& coeffRef(Index index)
     {
       EIGEN_STATIC_ASSERT_LVALUE(MatrixType)
       return derived().nestedExpression().const_cast_derived().coeffRef(index);