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Re: About the Operator '|' and the DCG Draft

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Subject: Re: About the Operator '|' and the DCG Draft
From: burse...@gmail.com (Mostowski Collapse)
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by: Mostowski Collapse - Sun, 10 Apr 2022 20:39 UTC

Yet another bug, which is even a test case from
the ISO core standard, its the 4-th example from
Table 6 - Equivalent Terms:

/* SWI-Prolog */
?- op(9,fy,fy), op(9,yf,yf).
true.
?- X = (fy 2 yf), write_canonical(X), nl.
yf(fy(2))
X = fy 2 yf.

On the other hand:

/* GNU Prolog */
?- op(9,fy,fy), op(9,yf,yf).
yes
?- X = (fy 2 yf), write_canonical(X), nl.
fy(yf(2))
X = fy 2 yf

My suspicion, in terms of
https://github.com/ridgeworks/pPEGpl/tree/main/Examples/SWIP-grammar

These here are probably wrong:

op_associativityEq(fy,yfx,left).
op_associativityEq(fy,yf,left).

Actually I don’t know exactly, I am new to this code. Whats
especially difficult for me, to specify a change, even if I
can locate the error, I don’t know what to do as a fix?

But I guess more extensive testing would be needed to find
all table errors. I have only spotted two, because of analogy
between yfx and yf. But maybe there are more nasty bugs?

Mostowski Collapse schrieb am Samstag, 9. April 2022 um 14:17:17 UTC+2:
> Can he use his SWIPL example to figure out whats going wrong here:
> /* SWI-Prolog */
> ?- op(9,fy,fy), op(9,yfx,yfx).
> true.
>
> ?- X = (fy 1 yfx 2), write_canonical(X), nl.
> yfx(fy(1),2)
> Maybe its just a small bug, like (>=)/2 instead of (>)/2 or somesuch.
>
> I am refering to:
> https://github.com/ridgeworks/pPEGpl/tree/main/Examples/SWIP-grammar
> Mostowski Collapse schrieb am Samstag, 9. April 2022 um 12:51:13 UTC+2:
> > Now I found a test case where SWI-Prolog and
> > Scryer Prolog differ in parsing:
> >
> > /* SWI-Prolog */
> > ?- op(9,fy,fy), op(9,yfx,yfx).
> > true.
> >
> > ?- X = (fy 1 yfx 2), write_canonical(X), nl.
> > yfx(fy(1),2)
> >
> > But then:
> >
> > /* Scryer Prolog */
> > ?- op(9,fy,fy), op(9,yfx,yfx).
> > true.
> >
> > ?- X = (fy 1 yfx 2), write_canonical(X), nl.
> > fy(yfx(1,2))
> >
> > Was worried what Dogelog Player does. But it seems Dogelog Player
> > sides with Scryer Prolog, also GNU Prolog, Tau Prolog and
> > formerly Jekejeke Prolog do.

Subject	Author
About the Operator '\|' and the DCG Draft	Mostowski Collapse

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devel / comp.lang.prolog / Re: About the Operator '|' and the DCG Draft