From Newsgroup: comp.lang.prolog
Interstingly SICStus Prolog, which is the sequel
to Quintus, does not impose the same restriction
as Scryer Prolog:
/* SICStus 4.9.0 */
| ?- current_op(X, Y, *).
X = 400,
Y = yfx ? ;
no
| ?- X = (* = *).
X = ((*)=(*)) ?
yes
So what went wrong in the ISO standard. There are so
many idiosyncratic things in the ISO standard, that
are only found in GNU Prolog. So they took GNU Prolog
as the template for the language syntax and ignored
all other Prolog systems? Its not 100% true. SICStus
Prolog has also some idiosyncratic things like:
/* SICStus 4.9.0 */
| ?- X = (- 1), write_canonical(X), nl.
-1
X = -1 ?
| ?- X = (-1), write_canonical(X), nl.
-1
X = -1 ?
Compare to SWI-Prolog:
/* SWI-Prolog 9.3.8 */
?- X = (- 1), write_canonical(X), nl.
-(1)
X = - 1.
?- X = (-1), write_canonical(X), nl.
-1
X = -1.
I like the SWI-Prolog behaviour better...
Mild Shock schrieb:
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
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