mpg-ref-predicate_property (SICStus Prolog)

11.3.159 `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

The skeletal specification of a loaded predicate.

PredProperty

term

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

one of the atoms built_in (for built-in predicates) or compiled or interpreted (for user defined predicates) or fd_constraint for FD predicates see Defining Primitive Constraints.
the atom dynamic for predicates that have been declared dynamic (see Dynamic Declarations),
the atom multifile for predicates that have been declared multifile (see Multifile Declarations),
the atom volatile for predicates that have been declared volatile (see Volatile Declarations),
the atom jittable for predicates that are amenable to JIT compilation,
the atom jitted for predicates that have been JIT compiled,
one or more terms (block Term) for predicates that have block declarations (see Block Declarations),
the atom exported or terms imported_from(ModuleFrom) for predicates exported or imported from modules (see ref-mod),
the term (meta_predicate Term) for predicates that have meta-predicate declarations (see ref-mod-met).

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, then 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 ;

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.

Exceptions

None.

11.3.159 predicate_property/2