Re: GUI was Re: why Ada is so unpopular ?

From: Warren W. Gay VE3WWG (warren_at_ve3wwg.tk)
Date: 01/22/04 

Date: Thu, 22 Jan 2004 12:48:28 -0500

Marin David Condic wrote:

> Wait a minute. Aren't directories usually considered to be some kind of
> tree structure? Doesn't MSVC++ and the MFC supply some kind of tree
> widget for displaying things like directories? Seems like every time I
> pop up a directory on Windows, I see something that looks very
> reminiscent of a tree and one that looks surprisingly like the one I
> seem to recall was in the MFC. Maybe I'm wrong, but it looks to me like
> Microsoft might just be keeping some kind of tree data structure in
> place for handling directories. Not that the fact that Microsoft does
> something necessarily makes a recomendation for doing the same - but it
> would seem like it might not be all that painful for some apps.

You're right, but this doesn't work very well when you drop
into a directory with thousands of files. A smart tree widget
might just peruse "directory portions", where the tree widget
is visible (perhaps a less than trivial exercise). But I suspect
they take the easy way out, and require all entries to be loaded
in to the widget's dynamic memory. Otherwise performance in large
directory cases would not be so abysmal.

> What would be wrong with a "Directories" package having a call that
> would return some kind of tree data structure?

The OP was referring to the fact that you cannot count on the fact
that you will have a limited number of directory entries returned.
The idea works if you insist on a "reasonable" sized directory.
But this is outside of your control.

This is much like insisting that an SQL query should always return
few enough rows, that can be held in the client program's memory.
Many programs get written without thinking ahead about this very
issue. Usually these short-sighted programs implement ok, but then
with time passing, and database growing, it is realized that
something else must be done about the original design. 

-- 
Warren W. Gay VE3WWG
http://ve3wwg.tk