Duration

- Implemented operator- for us by the Variant.

src/Duration.cpp

@@ -151,6 +151,13 @@ Duration& Duration::operator= (const Duration& other)
   return *this;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+Duration& Duration::operator- (const Duration& other)
+{
+  throw std::string ("Error: Duration::operator- unimplemented");
+  return *this;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 std::string Duration::format () const
 {