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portray_clause/1 does not emit operators correctly #2715

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triska opened this issue Dec 17, 2024 · 2 comments
Open

portray_clause/1 does not emit operators correctly #2715

triska opened this issue Dec 17, 2024 · 2 comments

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@triska
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triska commented Dec 17, 2024

Example:

?- portray_clause(((-) :- (-),(-))).
- :-
   - ,
   - .
triska added a commit to triska/scryer-prolog that referenced this issue Dec 17, 2024
@triska
use round brackets for goals involving operators
8dc80b8 
Examples:

    ?- portray_clause(((+) :- a=b,(-))).
    (+) :-
       a=b,
       (-).
       true.

    ?- portray_clause((a :- (b :- c))).
    a :-
       (b:-c).
       true.

This addresses mthom#2715.

Currently, more round brackets than needed are emitted. Ideally, a
better approach to solve the issue here and also in toplevel.pl is
found in the future.
@triska
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triska commented Dec 21, 2024

#2714 addresses this.

@triska triska closed this as completed Dec 21, 2024
@UWN
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UWN commented Dec 21, 2024

Now:

?- portray_clause(//).
   outputs("(//).\n"), unexpected.
   outputs("// .\n"). % expected, but not found

Justification: "//" is an atom which is an operator and thus has priority 1201 (6.3.1.3). The whole text is a valid clause term (6.2.1.2) because the priority for a clause term is 1201, too. As of today, only GNU Prolog writes this correctly, SICStus uses round brackets. And ignoring those that do not write round brackets for (//):-(//) or just write invalid syntax.

@triska triska reopened this Dec 21, 2024
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@triska @UWN