Oz and Mozart Users Mailing List

Re: "or" statement


From: Luis Quesada (luque@info.ucl.ac.be)
Date: Fri Sep 21 2001 - 16:51:16 CEST


Christian Schulte wrote:

> both Luis and Denys are right (how Salomonian of me ;-) ). Oz used to employ
> the top-commit rule (allow the disjunction to reduce with an entailed
> clause, provided its body is skip). However the current system does not
> implement it (their use seemed to be limited at that time).
>
> I begin to see that there is new and revived interest in combinators. Also
> it appears to me that we are lacking documentation of their semantics. Also,
> there have been questions raised regarding their semantics. I can only
> reassure that programming combinators is reasonably easy and getting at your
> favourite disjunction is simple -- this is the true advantage of spaces.
>
> So don't feel confined to the combinators that are there, build your own. If
> you are then convinced make a proposal of inclusion into the system.
>
> With other words: design, hack, discuss and contribute!
>
>

Totally agree with your encouragement! Let us try to put it into practice by
bringing an old issue between us back :-) . Even though I am very pleased with
the power of the current or (after accepting your invitation to use control
variables), I still keep the dream of counting on a combinator that behave
like the current or but also be able to do the following:

thread if X=1 then Y=2 end end
new_or
    X=1 Y=1
[]
    X=2
end

Given the scenario above, I would like that new_or reduce to X=2. In other
words, I would like to have an or able to see the threads of its parent.

Certainly, the first step is to start assimilating the current implementation.
However, I wonder whether the implementation of such a new combinator requires
from a space the ability to export its threads.

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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