Add member size in VectorSpaceOperation

  - VectorSpaceOperation <-1> corresponding to operations on dynamic size
    vectors now handles vectors of given size.

src/multibody/liegroup/vector-space.hpp

@@ -39,7 +39,27 @@ namespace se3
   struct VectorSpaceOperation : public LieGroupOperationBase <VectorSpaceOperation<Size> >
   {
     typedef VectorSpaceOperation<Size>  LieGroupDerived;
+
     SE3_LIE_GROUP_TYPEDEF_TEMPLATE;
+    typedef typename Eigen::Matrix <Scalar, 1, 1>::Index size_type;
+
+    /// Constructor
+    /// \param size size of the vector space: should be the equal to template
+    ///        argument for static sized vector-spaces.
+    VectorSpaceOperation (int size = Size) : size_ (size)
+    {
+      assert (size_ >= 0);
+      assert (Size == Eigen::Dynamic || size_ == Size);
+    }
+
+    size_type nq () const
+    {
+      return size_;
+    }
+    size_type nv () const
+    {
+      return size_;
+    }
 
     template <class ConfigL_t, class ConfigR_t, class Tangent_t>
     static void difference_impl(const Eigen::MatrixBase<ConfigL_t> & q0,
@@ -86,6 +106,8 @@ namespace se3
         res[i] = lower_pos_limit[i] + (( upper_pos_limit[i] - lower_pos_limit[i]) * rand())/RAND_MAX;
       }
     }
+  private:
+    size_type size_;
   }; // struct VectorSpaceOperation
 
 } // namespace se3