predicate_property/2

Synopsis

predicate_property(*Callable, *PredProperty)

Unifies PredProperty with a predicate property of an existing predicate, and Callable with the most general term that corresponds to that predicate.

Arguments

Callable callable [MOD]

the skeletal specification (see ref-syn-spc) of a loaded predicate

PredProperty term

the various properties associated with Callable. Each loaded predicate will have one or more of the properties:

Property

Comments

compiled

can have the multifile property

interpreted

can have either the dynamic or multifile property or both

built_in

multifile

dynamic

exported

on the public predicate list of its source module

imported_from(Module)

imported into the source module from Module )

foreign

meta_predicate(Term)

Term was specified in a meta_predicate declaration. Thus Term consists of the principal functor name followed by mode declarations for its arguments. For example:

               mysort(:, +, -)
               

See ref-mod-met for further information.

volatile

not to be saved in QOF files

locked

not visible in the debugger due to use of -h option to qpc

has_advice

advice has been added for the predicate

checking_advice

advice checking is enabled for the predicate

Description

• If Callable is instantiated then predicate_property/2 successively unifies PredProperty with the various properties associated with Callable.
• If PredProperty is bound to a valid predicate property, then predicate_property/2 successively unifies Callable with the skeletal specifications of all loaded predicates having PredProperty.
• If Callable is not a loaded predicate or PredProperty is not a valid predicate property, the call fails.
• If both arguments are unbound, then predicate_property/2 can be used to backtrack through all currently defined predicates and their corresponding properties.

Examples

• Predicates acquire properties when they are defined:

            | ?- [user].
            | :- dynamic p/1.
            | p(a).
            | end_of_file.
            % user compiled 0.117 sec 296 bytes
            
            yes
            | ?- predicate_property(p(_), Property).
            
            Property = (dynamic) ;
            
            Property = interpreted ;
            
            no
            

• To backtrack through all the predicates P imported into module m from any module:

            | ?- predicate_property(m:P, imported_from(_)).
            

• To backtrack through all the predicates P imported into module m1 from module m2:

            | ?- predicate_property(m1:P, imported_from(m2)).
            

• To backtrack through all the predicates P exported by module m:

            | ?- predicate_property(m:P, exported).
            

• A variable can also be used in place of a module atom to find the names of modules having a predicate and property association:

            | ?- predicate_property(M:f, imported_from(m1)).
            

  will return all modules M that import f/0 from m1.

Please note: All dynamic predicates are currently interpreted.

See Also

fileerrors/0, nofileerrors/0, gc/0, compile/1, module/[1,2], foreign/[2,3], meta_predicate/1, volatile/1, add_advice/3, check_advice/[0,1], current_predicate/2 ref-mod-ilm-vis