Re: [Boost-users] Auto dispatch metaprogramming tricks

Subject: Re: [Boost-users] Auto dispatch metaprogramming tricks
From: John Dlugosz (JDlugosz_at_[hidden])
Date: 2010-05-24 12:26:34

> It's building this set that's the problem, not checking if an item is
> in
> it.  I need a list of all messages IDs (UINTs) that have a
> message<BLAH>
> specialisation.

Why?  I mean, what is the difference between pro-actively declaring all the allowed forms and recognizing an allowed for if/when it is presented?

The trouble with "functional programming" is that you can't update a value.  At run-time, you can imagine a constructor adds the instance to a linked list of all live instances.  Compile-time MPL cannot do something similar: add itself to a list when a class is created.  There is no changeable list, in principle.

Perhaps you could have a script that greps for derived classes (some special marker you include to make it easy to notice) and generate another include file from that.

> Yes, this is how my handlers work (except the on() method is not itself
> a
> template - does that affect it?).

I don't know enough about it to answer.

> How do you match the incoming message ID to the pods?

[not Boost related]
A declared range that each "commission" might be interested in, and a return value from the "minister" that the message just presented will _never_ be handled (so don't bother asking again).

> ...
> I'm afraid I don't understand this bit.  What do you mean by specially
> declared functions?

Some details at <http://www.dlugosz.com/Repertoire/refman/Tomahawk/message_parliament_guide.htm>.

For example, process_MouseMove takes parameters that are specific to WM_MOUSEMOVE, not generic msg or lParam values.  It has a different signature than, say, process_Size (which handles WM_SIZE messages).

> 
> Thanks.
> Alex







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