Re: Child packages question

[tmoran@acm.org]

>We put all of the bindings in Claw into private packages
>(Claw.Low_Level.Windows, Claw.Low_Level.GDI, etc.). Only Claw can with
>those packages; users of Claw can't access them.
  But parent's normally don't call children.  In the Claw case, Claw.child
may call claw.low_level.xxx but that's calling a cousin.  I'd say the use
of child packages for private packages is a less common technique.  More
commonly a child package extends somehow its parent.  For instance,
claw.sockets has a bunch of stuff, but claw.sockets.non-blocking has
extensions for those times you want your sockets to be non-blocking.  It
can't be claw.sockets_non_blocking, "with"ing claw.sockets, because it
needs access to some things that the parent claw.sockets does not make
public.
  So usually children see parents, in more detail than the general public,
but parents don't see children.  The phraseology of parent/child/private
parts etc just doesn't work nicely, at least if you are thinking of
humans.  Perhaps there's a nicer animal model.
  If you want Car to see Car.Engine, you probably want Car.Engine to be
a package *inside* of Car, not a child of Car.  Then the two packages
can see (selectively) parts of each other.