Re: Order of cluster searching with ace file (recent snapshot)

Hi Oliver,

On 12/8/06, Oliver Elphick <[email protected]> wrote:
> a class that was in both local and system (in different versions) was
> chosen from system by compile and from local by finder.  Changing the
> order of clusters changes the result from finder but compile always
> chooses the system cluster.
>
> Do finder and compile use different search algorithms?

Not exactly. To answer to your question, I have first to explain how
class finding is working in the recent snapshots.

The aim is to allow more than one class to have the same name in the
system, while automatically resolve ambiguities without relying on
user parametry. In fact, the basic idea is that a group of classes (a
library, a framework, or an application) is self-consistent.
Therefore, when a class uses another class, it "expects" it to be the
one the author (of the classes bundle) thought of. There are two
cases:

 - either the author wrote the class. In that case he really wants
*that* class to be used, even if another class with the same name
exists within the system
 - or the author uses a standard class, or a library class, and of
course he should be able to do so.

To implement that, SmartEiffel now uses a notion of "class distance".
Class distance is just the reification of what I wrote above.
SmartEiffel starts looking for a class starting from the cluster of
its client. It goes down, then up; only then does it scan the whole
system.

The whole system is just a bunch of unrelated cluster trees, which
order is given by the ACE file (or implied by config if no ACE file is
used). Note that the -verbose flag in very recent snapshots displays
the whole system as it is computed using a tree display. There can be
more than one tree.

See the comments I added in a very recent snapshot, in
ACE.find_class_text (around line 690).

Now, the problem with finder is that it does not know this notion of
class distance. Distance from what?... So it just scans the whole
system and picks the first class it meets with the good name.

Does it mean that the new finding algorithm is bad? I don't think so.
To me, we must add an option to finder to tell it where to start
looking for the class. Another option would be for finder to display
by default all the classes with a given name. It's still WIP.

I hope my explanations are clear. All comments are welcome.

Best regards,
--=20
Cyril ADRIAN - http://www.cadrian.net/~cyril

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Ita MVSICA inter Artes Liberales
in medio radiat
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