Index: kernel/include/VectorD.h
===================================================================
--- kernel/include/VectorD.h	(revision 1068)
+++ kernel/include/VectorD.h	(working copy)
@@ -339,7 +339,24 @@
 }
 
 
+//! compute the squared distance between two vectors
 template <unsigned int D>
+Float get_squared_distance(const VectorD<D> &v1, const VectorD<D> &v2) {
+  Float d, s = 0;
+  for (unsigned int i=0; i< D; ++i) {
+    d = v1[i] - v2[i];
+    s += d*d;
+  }
+  return s;
+}
+
+// ! compute the distance between two vectors
+template <unsigned int D>
+Float get_distance (const VectorD<D> &v1, const VectorD<D> &v2) {
+  return std::sqrt(get_squared_distance(v1, v2));
+}
+
+template <unsigned int D>
 struct SpacesIO
 {
   const VectorD<D> &v_;