novaBBS - comp.lang.prolog - Re: About the Operator '|' and the DCG Draft

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

<t4ja44$1lfep$1@solani.org>

https://www.novabbs.com/devel/article-flat.php?id=9938&group=comp.lang.prolog#9938

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From: janbu...@fastmail.fm (Mostowski Collapse)
Newsgroups: comp.lang.prolog
Subject: Re: About the Operator '|' and the DCG Draft
Date: Sat, 30 Apr 2022 14:29:58 +0200
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by: Mostowski Collapse - Sat, 30 Apr 2022 12:29 UTC

This is an interesting pPEG example bug. Actually I wanted to hunt
parenthesis parsing bugs, so I was up to generating some test cases that
contain parenthesis. But this test case doesn’t contain any parenthesis,

but it seems a binary infix operator is parsed as an unary functor?

?- string_termList(":- x0 =:= :- x1 - x2 .", [Y]), write_canonical(Y), nl.
:-(:-(=:=(x0),-(x1,x2)))
Y = (:- (=:=(x0):-x1-x2)).

I am still using pPEG from 14.04.2022. How do I do a package update?

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

<t4ja5f$1lfep$2@solani.org>

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https://www.novabbs.com/devel/article-flat.php?id=9939&group=comp.lang.prolog#9939

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From: janbu...@fastmail.fm (Mostowski Collapse)
Newsgroups: comp.lang.prolog
Subject: Re: About the Operator '|' and the DCG Draft
Date: Sat, 30 Apr 2022 14:30:41 +0200
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In-Reply-To: <t4ja44$1lfep$1@solani.org>

by: Mostowski Collapse - Sat, 30 Apr 2022 12:30 UTC

Concerning parenthesis I only found this bug, but its not
really parenthesis related. So unlike Trealla it could be
that parenthesis are not a problem. This here gives the same

associativity hickup with and without parenthesis:

?- string_termList("- ( x0 * x1 ) ** x2 =:= x3 .", [Y]),
write_canonical(Y), nl.
-(=:=(**(*(x0,x1),x2),x3))
Y = - ((x0*x1)**x2=:=x3).

?- string_termList("- x4 ** x2 =:= x3 .", [Y]), write_canonical(Y), nl.
-(=:=(**(x4,x2),x3))
Y = - (x4**x2=:=x3).

?- Y = (- x4 ** x2 =:= x3), write_canonical(Y), nl.
=:=(-(**(x4,x2)),x3)
Y = (-x4**x2=:=x3).

Mostowski Collapse schrieb:
> This is an interesting pPEG example bug. Actually I wanted to hunt
> parenthesis parsing bugs, so I was up to generating some test cases that
> contain parenthesis. But this test case doesn’t contain any parenthesis,
>
> but it seems a binary infix operator is parsed as an unary functor?
>
> ?- string_termList(":- x0 =:= :- x1 - x2 .", [Y]), write_canonical(Y), nl.
> :-(:-(=:=(x0),-(x1,x2)))
> Y = (:- (=:=(x0):-x1-x2)).
>
> I am still using pPEG from 14.04.2022. How do I do a package update?

All your files have been destroyed (sorry). Paul.

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

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