CODEWITHSUNDEEP
moduleprologoperatorsswi-prolog
David Tonhofer
David Tonhofer

Reputation: 15316

How do I find out which module a Prolog operator comes from?

This may be specific to SWI-Prolog.

How can I ask the system which module a predicate comes from?

For predicates, one can use predicate_property/2:

?-
predicate_property(is_ordset(_),imported_from(M)).
M = ordsets.

Ok, so is_ordset/2 comes from module ordsets.

I can also ask for the specific file that defines that module:

?-
predicate_property(is_ordset(_),file(F)).
F = '/usr/local/logic/swipl/lib/swipl/library/ordsets.pl'.

But how to do the same for operators, which may be defined in and exported from modules in the same way as predicates, at least in SWI-Prolog?

Upvotes: 1

Views: 154

Answers (1)

Paulo Moura
Paulo Moura

Reputation: 18663

SWI-Prolog is one of the few Prolog systems where operators can be local to modules. A possible solution (but not ideal from a performance perspective) to find which module exported an operator is:

?- current_module(M),
   module_property(M, exported_operators(Operators)),
   member(Operator, Operators).

For example:

?- use_module(library(clpfd)).
true.

?- current_module(M),
   module_property(M, exported_operators(Operators)),
   member(op(Priority, Type, '#>'), Operators).
M = clpfd,
Operators = [op(760, yfx, #<==>), op(750, xfy, #==>), op(750, yfx, #<==), op(740, yfx, #\/), op(730, yfx, #\), op(720, yfx, #/\), op(710, fy, #\), op(700, xfx, #>), op(..., ..., ...)|...],
Priority = 700,
Type = xfx .

There might be a better solution...

Upvotes: 1

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