Actually I arried at the conclusion, that the *receiving* of
a diff representation is actually a typical double-dispatch situation.
This leads to the attempt to come up with a specialised visitor
as standard pattern to handle and apply a diff. Obviously,
we do not want the classical GoF-Visitor, but (yes, we had
that discussion allready) -- well in terms of runtime cost,
we have to deal with at least two indirections anyway;
so now I'm exploring the idea to implement one of these
indirections through a functor object, which at the same time
acts as "Tag" in the diff representation language (instead
of using an enum as tag)
benefits of using a newer compiler, yay!
Explanation: the Link<...> template combines
various policy templates and exposes a set
of functions, which can be bound as functor
into an concrete time::Control instance.
Actually, we need to mix in only the Mutation
baseclass, because we just want to inherit
the privilege to change time values, which
are otherwise immutable. We don't need to
mix in the Mutator template anymore (this
was a leftover from an earlier design)
removed that inheritance relation; it was a typical
example of abusing inheritance and violated the
Liscov substitution principle. It is sufficient
to allow promotion of an offset into a Duration.
Note: Duration is the time metric
