add important comment and move stride helpers to DenseCoeffsBase.h

1 files changed, 29 insertions, 0 deletions

diff --git a/Eigen/src/Core/DenseCoeffsBase.h b/Eigen/src/Core/DenseCoeffsBase.h
index faebc0b14..d79b5c107 100644
--- a/Eigen/src/Core/DenseCoeffsBase.h
+++ b/Eigen/src/Core/DenseCoeffsBase.h
@@ -214,6 +214,11 @@ class DenseCoeffsBase : public EigenBase<Derived>
     }
 
   protected:
+    // explanation: DenseBase is doing "using ..." on the methods from DenseCoeffsBase.
+    // But some methods are only available in the EnableDirectAccessAPI case.
+    // So we add dummy methods here with these names, so that "using... " doesn't fail.
+    // It's not private so that the child class DenseBase can access them, and it's not public
+    // either since it's an implementation detail, so has to be protected.
     void coeffRef();
     void coeffRefByOuterInner();
     void writePacket();
@@ -570,4 +575,28 @@ inline static int ei_first_aligned(const Derived& m)
           ::run(m);
 }
 
+template<typename Derived, bool HasDirectAccess = ei_has_direct_access<Derived>::ret>
+struct ei_inner_stride_at_compile_time
+{
+  enum { ret = ei_traits<Derived>::InnerStrideAtCompileTime };
+};
+
+template<typename Derived>
+struct ei_inner_stride_at_compile_time<Derived, false>
+{
+  enum { ret = 0 };
+};
+
+template<typename Derived, bool HasDirectAccess = ei_has_direct_access<Derived>::ret>
+struct ei_outer_stride_at_compile_time
+{
+  enum { ret = ei_traits<Derived>::OuterStrideAtCompileTime };
+};
+
+template<typename Derived>
+struct ei_outer_stride_at_compile_time<Derived, false>
+{
+  enum { ret = 0 };
+};
+
 #endif // EIGEN_COEFFS_H