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From: Mild Shock <janburse@fastmail.fm>
Newsgroups: comp.lang.prolog
Subject: Re: Why cant Scryer Prolog parse this? (Was: France is the Fire
 Nation of Prolog)
Date: Sun, 1 Sep 2024 16:29:12 +0200
Message-ID: <vb1tno$21359$1@solani.org>
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Ok, my bad, prefix (table) is probably
not the best example. This example works better:

scryer-prolog$ target/release/scryer-prolog
?- X = (#\/ = #\/).
    X = (#\/ = #\/).
?- use_module(library(clpz)).
    true.
?- X = (#\/ = #\/).
    error(syntax_error(incomplete_reduction),read_term/3:1).

versus:

trealla$ ./tpl
?- X = (#\/ = #\/).
    X = (#\/ = #\/) .
?- use_module(library(clpz)).
    true.
?- X = (#\/ = #\/).
    X = ((#\/)=(#\/)).

Mild Shock schrieb:
> Tau Prolog can do it:
> 
> https://github.com/tau-prolog/tau-prolog/issues/286
> 
> But Tau Prolog is dead now, or hibernating for
> more than 12 months already. So the more lenient
> behaviour has already been ossified in this Prolog system.
> 
> Another argument not in favor, it also makes parsing
> more non-monotonic, if you introduce the "shall" condition,
> because its a negative parsing condition.
> ```
> $ target/release/scryer-prolog
> ?- X = (table = table).
>     X = (table=table).
> 
> ?- use_module(library(tabling)).
>     true.
> 
> ?- X = (table = table).
>     error(syntax_error(incomplete_reduction),read_term/3:1).
> ```
> Maybe introducing more than rather less operator table
> dependencies in a grammar is always a mistake? A further
> use case is (!)/1 in TPTP syntax.
> 
> Mild Shock schrieb:
>> Hi,
>>
>> Why cant Scryer Prolog parse this?
>>
>> scryer-prolog$ target/release/scryer-prolog -v
>> v0.9.4-165-g12a61cdf
>>
>> scryer-prolog$ target/release/scryer-prolog
>>
>> ?- current_op(X, Y, *).
>>     X = 400, Y = yfx.
>>
>> ?- X = (* = *).
>>     error(syntax_error(incomplete_reduction),read_term/3:1).
>>
>> On the other hand Trealla Prolog has no problem:
>>
>> trealla$ ./tpl -v
>> Trealla Prolog (c) Infradig 2020-2024, v2.55.31
>>
>> trealla$ ./tpl
>> ?- current_op(X, Y, *).
>>     X = 400, Y = yfx.
>>
>> ?- X = (* = *).
>>     X = ((*)=(*)).
>>
>> What LEX / YACC did they use? Holy cow!
>>
>> Bye
>>
>> Mild Shock schrieb:
>>> Is Canada also France? Seems I am not the only one who got
>>> into struggle with Logtalk sooner or later. LoL
>>>
>>> How its started:
>>> Ticket raised by me Aug 9, 2021 (when I was "ghost")
>>> Feature request flag dialect, maybe version and version_data
>>> https://github.com/mthom/scryer-prolog/issues/1017
>>>
>>> How its going:
>>> Commit by pmoura last week
>>> Delete Scryer Prolog support due to this system refusal to
>>> support the de facto standard `version_data` flag
>>> https://github.com/LogtalkDotOrg/logtalk3/commit/d93883c5a8b014af09bd0e11439eaff30e1c1a5c 
>>>
>>>
>>> What happened?
>>>
>>> LoL
>>>
>>
>