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?

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?

I didn’t start a new testing campaign with pPEG yet, where I get
a new type of error, which I do not yet know how to silence.
But meanwhile I have a funny test case where

SWI-Prolog and SICStus disagree:

/* SWI-Prolog */
?- X = (- - - * - - - x0), write_canonical(X), nl.
*(-(-(-)),-(-(-(x0))))
X = - - (-)* - - -x0.

/* SICStus Prolog */
?- X = (- - - * - - - x0), write_canonical(X), nl.
-(-(-(-(*))),-(-(x0)))
X = - - - (*)- - -x0 ?

The SWI-Prolog built-in with_output_to/2 does also not work.
Would need something like a with_error_to/2 ?
Does this exist? I only get:

?- with_output_to(atom(_), (write('I am chatty'), nl)).
true.

?- with_output_to(atom(_), string_termList("- x4 ** x2 =:= .", [Y])).
% pPEG Error: Prolog.expr failed, expected Prolog.expr at line 1.16:
% 1 | - x4 ** x2 =:= .
% ^
false.

Mostowski Collapse schrieb am Montag, 2. Mai 2022 um 16:48:56 UTC+2:
> I didn’t start a new testing campaign with pPEG yet, where I get
> a new type of error, which I do not yet know how to silence.
> But meanwhile I have a funny test case where
>
> SWI-Prolog and SICStus disagree:
>
> /* SWI-Prolog */
> ?- X = (- - - * - - - x0), write_canonical(X), nl.
> *(-(-(-)),-(-(-(x0))))
> X = - - (-)* - - -x0.
>
> /* SICStus Prolog */
> ?- X = (- - - * - - - x0), write_canonical(X), nl.
> -(-(-(-(*))),-(-(x0)))
> X = - - - (*)- - -x0 ?

My parser research has arrived at this eclectic challenge.
Here is an example where I can coerce both SWI-Prolog and
pPEG SWIPL Example into masking the real error.

Here is what ECLiPSe Prolog does:

[eclipse 1]: X = foo = bar = baz = 'ab\qc' .
syntax error: bracket necessary
| X = foo = bar = baz = 'ab\qc' .
| ^ here

And here is SWI-Prolog and pPEG SWIPL Example:

?- X = foo = bar = baz = 'ab\qc' .
ERROR: Syntax error: Unknown character escape in quoted atom or string: `\q'
ERROR: X = foo = bar = baz = 'ab
ERROR: ** here **
ERROR: \qc' .

?- string_termList("X = foo = bar = baz = 'ab\\qc' .", [T]).
% pPEG Error: _esc failed, ...
% 1 | X = foo = bar = baz = 'ab\qc' .
% ^
false.

It seems Scryer Prolog is not that advanced like ECLiPSe Prolog:

$ target/release/scryer-prolog
?- X = foo = bar = baz = 'ab\qc' .
error(syntax_error(invalid_single_quoted_character),read_term/3).

Initially my thought was my monadic parser from Dogelog player
will automatically be able to deal with this. But its non-trivial.
But my Dogelog player got a scanner/parser booster yesterday:

?- X = foo = bar = baz = 'ab\qc' .
error(syntax_error(operator_clash), [user:1])
Mostowski Collapse schrieb am Dienstag, 17. Mai 2022 um 23:34:51 UTC+2:
> My parser research has arrived at this eclectic challenge.
> Here is an example where I can coerce both SWI-Prolog and
> pPEG SWIPL Example into masking the real error.
>
> Here is what ECLiPSe Prolog does:
>
> [eclipse 1]: X = foo = bar = baz = 'ab\qc' .
> syntax error: bracket necessary
> | X = foo = bar = baz = 'ab\qc' .
> | ^ here
>
> And here is SWI-Prolog and pPEG SWIPL Example:
>
> ?- X = foo = bar = baz = 'ab\qc' .
> ERROR: Syntax error: Unknown character escape in quoted atom or string: `\q'
> ERROR: X = foo = bar = baz = 'ab
> ERROR: ** here **
> ERROR: \qc' .
>
> ?- string_termList("X = foo = bar = baz = 'ab\\qc' .", [T]).
> % pPEG Error: _esc failed, ...
> % 1 | X = foo = bar = baz = 'ab\qc' .
> % ^
> false.

Now I have a new project going. I need a better microscope
to find differences in parsing of the different Prolog systems.
So that I might generate a phylogenic tree.

I see a trend against ECliPSe Prolog concering fuzz3, now also
results available for Scryer Prolog and Trealla Prolog. Unfortunately
no data yet available for Tau Prolog, still waiting

for charsio from Tau Prolog:

ECLiPSe Scryer Trealla
fuzz3 292 0 0
fuzz4 382 801 532

My suspicion, for fuzz4, Scryer Prolog behaves like GNU Prolog,
not shown here, but GNU Prolog has same figures. But this would
need a distance matrice, to get some support for this hypothesis,

that they are really the same.

Mostowski Collapse schrieb am Dienstag, 17. Mai 2022 um 23:37:12 UTC+2:
> It seems Scryer Prolog is not that advanced like ECLiPSe Prolog:
>
> $ target/release/scryer-prolog
> ?- X = foo = bar = baz = 'ab\qc' .
> error(syntax_error(invalid_single_quoted_character),read_term/3).
>
> Initially my thought was my monadic parser from Dogelog player
> will automatically be able to deal with this. But its non-trivial.
> But my Dogelog player got a scanner/parser booster yesterday:
> ?- X = foo = bar = baz = 'ab\qc' .
> error(syntax_error(operator_clash), [user:1])
> Mostowski Collapse schrieb am Dienstag, 17. Mai 2022 um 23:34:51 UTC+2:
> > My parser research has arrived at this eclectic challenge.
> > Here is an example where I can coerce both SWI-Prolog and
> > pPEG SWIPL Example into masking the real error.
> >
> > Here is what ECLiPSe Prolog does:
> >
> > [eclipse 1]: X = foo = bar = baz = 'ab\qc' .
> > syntax error: bracket necessary
> > | X = foo = bar = baz = 'ab\qc' .
> > | ^ here
> >
> > And here is SWI-Prolog and pPEG SWIPL Example:
> >
> > ?- X = foo = bar = baz = 'ab\qc' .
> > ERROR: Syntax error: Unknown character escape in quoted atom or string: `\q'
> > ERROR: X = foo = bar = baz = 'ab
> > ERROR: ** here **
> > ERROR: \qc' .
> >
> > ?- string_termList("X = foo = bar = baz = 'ab\\qc' .", [T]).
> > % pPEG Error: _esc failed, ...
> > % 1 | X = foo = bar = baz = 'ab\qc' .
> > % ^
> > false.

I made a kind of phylogenetic tree, the numbers in it indicate
how many test cases the various Prolog systems agree.
The results for fuzz4 are as follows:

?- pairing([eclipse4,gnu4,jekejeke4,swi4,scryer4,sicstus4,
ppeg4,trealla4], R), show(R, 0).
+--- 8713
+--- 9509
+--- trealla4
+--- 9997
+--- scryer4
+--- gnu4
+--- 9288
+--- 9586
+--- 9860
+--- eclipse4
+--- swi4
+--- jekejeke4
+--- 9642
+--- ppeg4
+--- sicstus4

SWI-Prolog is close to ECLiPSe Prolog in fuzz4 test cases. But pPEG
SWIPL Example is close to SICStus Prolog in fuzz4 test cases.

And my suspicion got confirmed, Scryer and GNU
do the same in fuzz4 test cases, except for a

few amusing strange results:

$ target/release/scryer-prolog -v
"v0.9.0-146-g25418db2-modified"
$ target/release/scryer-prolog
?- X = (- ( ( ) =:= x0).
X = (- '('=:=x0).
?- X = (- ( ( ) , x0).
X = (- '(',x0).
?- X = ( ( ( ) :- x0).
X = ('(':-x0).

LoL

Mostowski Collapse schrieb:
> I made a kind of phylogenetic tree, the numbers in it indicate
> how many test cases the various Prolog systems agree.
> The results for fuzz4 are as follows:
>
> ?- pairing([eclipse4,gnu4,jekejeke4,swi4,scryer4,sicstus4,
> ppeg4,trealla4], R), show(R, 0).
> +--- 8713
> +--- 9509
> +--- trealla4
> +--- 9997
> +--- scryer4
> +--- gnu4
> +--- 9288
> +--- 9586
> +--- 9860
> +--- eclipse4
> +--- swi4
> +--- jekejeke4
> +--- 9642
> +--- ppeg4
> +--- sicstus4
>
> SWI-Prolog is close to ECLiPSe Prolog in fuzz4 test cases. But pPEG
> SWIPL Example is close to SICStus Prolog in fuzz4 test cases.
>

Ok, this was fun:

Phylogenetic Trees for Prolog Operator Parsers
https://twitter.com/dogelogch/status/1528118780890603522

Phylogenetic Trees for Prolog Operator Parsers
https://www.facebook.com/groups/dogelog

Mostowski Collapse schrieb am Samstag, 21. Mai 2022 um 15:21:49 UTC+2:
> And my suspicion got confirmed, Scryer and GNU
> do the same in fuzz4 test cases, except for a
>
> few amusing strange results:
>
> $ target/release/scryer-prolog -v
> "v0.9.0-146-g25418db2-modified"
> $ target/release/scryer-prolog
> ?- X = (- ( ( ) =:= x0).
> X = (- '('=:=x0).
> ?- X = (- ( ( ) , x0).
> X = (- '(',x0).
> ?- X = ( ( ( ) :- x0).
> X = ('(':-x0).
>
> LoL
>
> Mostowski Collapse schrieb:
> > I made a kind of phylogenetic tree, the numbers in it indicate
> > how many test cases the various Prolog systems agree.
> > The results for fuzz4 are as follows:
> >
> > ?- pairing([eclipse4,gnu4,jekejeke4,swi4,scryer4,sicstus4,
> > ppeg4,trealla4], R), show(R, 0).
> > +--- 8713
> > +--- 9509
> > +--- trealla4
> > +--- 9997
> > +--- scryer4
> > +--- gnu4
> > +--- 9288
> > +--- 9586
> > +--- 9860
> > +--- eclipse4
> > +--- swi4
> > +--- jekejeke4
> > +--- 9642
> > +--- ppeg4
> > +--- sicstus4
> >
> > SWI-Prolog is close to ECLiPSe Prolog in fuzz4 test cases. But pPEG
> > SWIPL Example is close to SICStus Prolog in fuzz4 test cases.
> >