Re: New PAKCS release (Version 1.8.0)

From: Juan Carlos GOnzález Moreno <jcmoreno_at_ei.uvigo.es>
Date: Fri, 30 Mar 2007 10:33:51 +0200

HI,
        I am agree with Francisco considerations.

Best regards

El 29/03/2007, a las 20:23, Francisco Javier López Fraguas escribió:

>
>
>
> Michael Hanus wrote:
>
> >However, an implementation is free to do some optimizations,
> >e.g., inlining, constant propagation, partial evaluation,
> >or omitting eta-expansion so that reductions can be done earlier.
>
> Removing eta expansion is not merely an optimization,
> but has subtle semantic consequences in presence of non-determinism.
>
> The following is a well-known example for the CRWL (Toy) community:
>
> Consider the program
>
> g x = 0
> h x = 1
>
> fcoin = g
> fcoin = h % fcoin is a 'functional coin'
>
> fadd f g x = (f x) + (g x)
> fdouble f = fadd f f
>
> Now consider the evaluation of (fdouble fcoin 0)
> * Without eta expansion in the definition of fcoin
> (fdouble fcoin 0) returns 0 and 2
> * With eta expansion in the definition of fcoin, it returns 0,1 y 2
>
> Thus, performing eta expansion allows to 'escape from sharing'.
> I used to exploit this kind of properties in my postdoc lectures
> to illustrate
> how to simulate runtime choice in Toy.
>
> So, I strongly recommend to eliminate in the Curry report the
> paragraph
> mentioned by Wolfgang. Otherwise the report will not correspond to
> the behavior
> of the system.
>
> Wrt HO patterns, I will be glad if the FLP community adopt
> more widely the CRWL approach for HO.
>
> Best,
>
> Paco
>
> PS: Sorry, but I cannot react to new messages until April 10
>
> ----- Mensaje original -----
> De: Michael Hanus <mh_at_informatik.uni-kiel.de>
> Fecha: Jueves, Marzo 29, 2007 4:58 pm
> Asunto: Re: New PAKCS release (Version 1.8.0)
> A: Wolfgang Lux <wlux_at_uni-muenster.de>
> CC: curry_at_informatik.rwth-aachen.de
>
> > Wolfgang Lux wrote:
> > > Do you consider removing the sentence
> > > For convenience, a defining equation f = g
> > between functions
> > > is allowed but will be interpreted in Curry
> > as syntactic sugar
> > > for the corresponding defining equation f x
> > = g x on base types.
> > > on the bottom of p.6 from the report, which IMO suggests
> > > eta-expansion?
> >
> > I don't think that removing this sentence is a necessary
> requirement.
> > The original motivation for this sentence was to base the kernel
> > of Curry (i.e., without syntactic sugar) on a firm foundation,
> > i.e., needed narrowing or CRWL which were originally defined
> > only for first-order rewrite systems.
> >
> > However, an implementation is free to do some optimizations,
> > e.g., inlining, constant propagation, partial evaluation,
> > or omitting eta-expansion so that reductions can be done earlier.
> >
> > Since time has changed and there are extensions of CRWL
> > for higher-order rewrite systems (i.e., rules where the
> > left- and right-hand side are not of base type and
> > partial applications as patterns), I don't see a problem to
> > drop this sentence (i.e., the first-order interpretation of
> > higher-order rules). Moreover, we could also allow
> > partial applications as patterns (as in TOY).
> >
> > What do you think?
> >
> > Best regards,
> >
> > Michael
> >
> > _______________________________________________
> > curry mailing list
> > curry_at_lists.RWTH-Aachen.DE
> > http://MailMan.RWTH-Aachen.DE/mailman/listinfo/curry
> >
> >
>
> ********************************
> Francisco J. Lopez Fraguas
> Dep. Sistemas Informaticos y Computacion
> Fac. Informatica U. Complutense Madrid
> Prof. Jose Garcia Santesmases s/n
> 28040 Madrid
> Spain
>
> fraguas_at_sip.ucm.es
> Tel: +34 91 3947630
> Fax: +34 91 3947529
> ********************************
>
>
> _______________________________________________
> curry mailing list
> curry_at_lists.RWTH-Aachen.DE
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Dr. Juan Carlos González Moreno
Coordinador del Programa de Doctorado
Tecnologías avanzadas para el desarrollo de software inteligente
Dpto. Informática
Universidad de Vigo
jcmoreno_at_uvigo.es






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Received on Fri Mar 30 2007 - 13:23:50 CEST

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