alpha 3.1. in this commit:

- finally get the Eval stuff right. get back to having Eval as
  a subclass of Matrix with limited functionality, and then,
  add a typedef MatrixType to get the actual matrix type.
- add swap(), findBiggestCoeff()
- bugfix by Ramon in Transpose
- new demo: doc/echelon.cpp

Eigen/src/Core/Map.h

@@ -44,7 +44,8 @@ template<typename MatrixType> class Map
 {
   public:
     typedef typename MatrixType::Scalar Scalar;
-    friend class MatrixBase<Scalar, Map<MatrixType> >;
+    friend class MatrixBase<Scalar, Map>;
+    typedef MatrixBase<Scalar, Map> Base;
 
   private:
     enum {