Oz and Mozart Users Mailing List

Re: "or" statement


From: Luis Quesada (luque@info.ucl.ac.be)
Date: Thu Sep 20 2001 - 10:26:35 CEST


Denys Duchier wrote:

> jorgemp@icmc.sc.usp.br writes:
>
> > I just thought that one entailed guard is enough, isn't it?
>
> Of course not: you cannot commit to a clause until all others are
> disentailed. Remember the full syntax:
>
> or G1 then F1
> [] G2 then F2
> ...
> [] Gn then Fn
> end
>
> if G2 through Gn are disentailed, then the `or' reduces to
> G1 F1 (modulo some tricky details of concurrency in the G1).
> In cases where there remains more than one non-disentailed guard, the
> `or' continues to block.
>

It is clear that to keep the semantics of the or things should be in that
way. However, once it is known a guard of the or is entailed I just see two
options:

1. The or commits to the entailed option, which would not add any new
information to the store.
2. The or keeps suspended for ever , which would not add anything new
neither.

Could you please explain the benefits of leaving the or alive?

Luis

--
Catholic University of Louvain
Department of Computing Science and Engineering
Place Sainte Barbe, 2
B-1348 Louvain-la-Neuve, Belgium
Phone: (++32) (10) 47 90 13
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E-mail: luque@info.ucl.ac.be

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