- rework the coefficients API

- make vectors use a separate loop unroller, so that copying a
row-vector into a col-vector is now possible
- add much more documentation
- misc improvements

doc/examples/class_Cast.cpp

@@ -0,0 +1,23 @@
+#include <Eigen/Core.h>
+USING_PART_OF_NAMESPACE_EIGEN
+using namespace std;
+
+template<typename Scalar, typename Derived>
+Eigen::Cast<double, Derived>
+castToDouble(const MatrixBase<Scalar, Derived>& m)
+{
+  return Eigen::Cast<double, Derived>(m.ref());
+  // note: tempting as it is, writing "m.cast<double>()" here
+  // causes a compile error with g++ 4.2, apparently due to
+  // g++ getting confused by the many template types and
+  // template arguments involved.
+}
+
+int main(int, char**)
+{
+  Matrix2i m = Matrix2i::random();
+  cout << "Here's the matrix m. It has coefficients of type int."
+       << endl << m << endl;
+  cout << "Here's 0.05*m:" << endl << 0.05 * castToDouble(m) << endl;
+  return 0;
+}