Oz and Mozart Users Mailing List

Re: "or" statement


From: Denys Duchier (Denys.Duchier@ps.uni-sb.de)
Date: Wed Sep 19 2001 - 20:35:01 CEST


jorgemp@icmc.sc.usp.br writes:

> My real question was right at the beginning and primarily regarded
> matters of efficiency/implementation: what _really_ happens when a
> subspace is entailed? Does that relieve any of the load of the or
> statement? For I think it should, once it is then ensured that such
> a statement will never reduce nor have any effect on the original
> (parent) space.

The full syntax for the `or' statement is:

        or G1 then F1
        [] G2 then F2
        ...
        [] Gn then Fn
        end

If you have 2 guards entailed, which clause should you commit to? The
semantics of `or' is given in terms of disentailment and unit commit.
If what you mean is that whenever an `or' has two guards which are
entailed it should be destroyed and replaced by the much simpler and
just as infinitely blocking {Wait _}, then you'll be happy to know
that that's actually what the implementation does :-)

Cheers,

-- 
Dr. Denys Duchier			Denys.Duchier@ps.uni-sb.de
Forschungsbereich Programmiersysteme	(Programming Systems Lab)
Universitaet des Saarlandes, Geb. 45	http://www.ps.uni-sb.de/~duchier
Postfach 15 11 50			Phone: +49 681 302 5618
66041 Saarbruecken, Germany		Fax:   +49 681 302 5615
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