Re: Definitions

From: Zix (zix6_at_yahoo.com)
Date: 10/20/03 

Date: 20 Oct 2003 09:08:15 -0700

rackri@yahoo.it (rackri) wrote in message news:<7a2f224b.0310190050.39f26b50@posting.google.com>...
> Hi all,
>
> can you please help me to understand these concepts:
>
> - delegation
> - forwarding
> - indirection
> - redirection
> - double-dispatch
>
> Thanks -- Roberto

let's tackle a couple of these:

delegation: is a design time tradeoff between inheritance from or
"delegating" the desired functionality to another class. In building
a car object, you would delegate the braking functionality to a brake
object rather than inheriting off a brake class.

forwarding: not too sure about this one, but I take it to mean serving
as an intermediary between objects where the calls to an object get
routed or "forwarded" to another object. A Proxy (Design
Patterns,Gamma,etal) eventually "forwards" calls to the object that it
is stanging in for.

indirection: is a low level programming construct in which a storage
location, instead of holding a value, contains an address to another
location where the value is stored.

redirection: not really sure about this one, but in C++/C you can
redirect things like ostreams to stdout, stderr, files,etc. So I
would say that redirection is the ability to re-route information
to/from a source/sink.

double-dispatch: Alexandrescu defines (mulimethods/multiple dispatch)
as the ability to dispatch a function call based on the dynamic types
of multiple objects involved in the call (Modern C++ Design,
pp,263-264). 2 objects gives you double dispatch. The distinction
between types can be made either at compile or run-time.

oops, I tackled all of these, this sort of smells as a homework
problem (note to OP, let us see your take on these, you'll get a
better response), but I'm interested as to what others have to say.

Relevant Pages

  • Re: Definitions
    ... Class A requests Class B to perform an operation that is integral to the ... The reason the operation is essential to Class A is because delegation ... Forwarding is the passing along of data or activation signalfrom one ... "Indirection" is when Class A invokes, dispatches to a method on Class B ...
    (comp.object)
  • Re: Definitions
    ... > delegation: is a design time tradeoff between inheritance from or ... Redirection is what one does with "indirection". ... But before you manage dependency, ... dependency, managing the offering and procurement of services by, at ...
    (comp.object)
  • Re: remote desktop listening port and drive porting
    ... Try also forwarding UDP 3390... ... or COM port redirection for the server machine whose listening port was ... etc. just the client's drives to not appear on the remote desktop ...
    (microsoft.public.windowsxp.work_remotely)
  • Re: Primary DNS causes Web Page to Refresh constantly - why not forward?
    ... Leon E. Webster, MCSE commented ... > forwarding or delegation? ...
    (microsoft.public.win2000.dns)
  • OT (maybe) DNS delagation on RH9
    ... I have a DNS server running RH9 and Bind 9. ... At a basic level the delegation is working. ... If forwarding is enabled all queries for "corp.company.com" go to the ... Below is the protion of named.conf and the zone file: ...
    (RedHat)