Predicate information

7.8 Predicate information

7.8.1 `current_predicate/1`

Templates

: current_predicate(?predicate_indicator)

Description

current_predicate(Pred) succeeds if there exists a predicate indicator of a defined procedure that unifies with Pred. All user defined procedures are found, whether static or dynamic. Internal system procedures whose name begins with ’$’ are not found. A user-defined procedure is found even when it has no clauses. A user-defined procedure is not found if it has been abolished. To conform to the ISO reference, built-in predicates are not found except if the strict_iso Prolog flag is switched off (section 7.22.1). This predicate is re-executable on backtracking.

Errors


`Pred` is neither a variable nor a predicate indicator		`type_error(predicate_indicator, Pred)`

`Pred` is a term `Name/Arity` and `Arity` is neither a variable nor an integer		`type_error(integer, Arity)`

`Pred` is a term `Name/Arity` and `Name` is neither a variable nor an atom		`type_error(atom, Name)`

`Pred` is a term `Name/Arity` and `Arity` is an integer < 0		`domain_error(not_less_than_zero, Arity)`

`Pred` is a term `Name/Arity` and `Arity` is an integer > `max_arity` flag (section 7.22.1)		`representation_error(max_arity)`

Portability

ISO predicate.

7.8.2 `predicate_property/2`

Templates

: predicate_property(?predicate_indicator, ?predicate_property)

Description

predicate_property(Pred, Property) succeeds if there exists a predicate indicator of a defined procedure that unifies with Pred and if Property unifies with one of the properties of the procedure. All user defined procedures and built-in predicates are found. Internal system procedures whose name begins with ’$’ are not found. This predicate is re-executable on backtracking.

Predicate properties:

static: if the procedure is static.
dynamic: if the procedure is dynamic.
private: if the procedure is private.
public: if the procedure is public.
user: if the procedure is a user-defined procedure.
built_in: if the procedure is a Prolog built-in predicate.
built_in_fd: if the procedure is an FD built-in predicate.
native_code: if the procedure is compiled in native code.
prolog_file(File): source file from which the predicate has been read.
prolog_line(Line): line number of the source file.

Errors


`Pred` is neither a variable nor a predicate indicator		`type_error(predicate_indicator, Pred)`

`Pred` is a term `Name/Arity` and `Arity` is neither a variable nor an integer		`type_error(integer, Arity)`

`Pred` is a term `Name/Arity` and `Name` is neither a variable nor an atom		`type_error(atom, Name)`

`Pred` is a term `Name/Arity` and `Arity` is an integer < 0		`domain_error(not_less_than_zero, Arity)`

`Pred` is a term `Name/Arity` and `Arity` is an integer > `max_arity` flag (section 7.22.1)		`representation_error(max_arity)`

`Property` is neither a variable nor a predicate property term		`domain_error(predicate_property, Property)`

`Property` = `prolog_file(File)` and `File` is neither a variable nor an atom		`type_error(atom, File)`

`Property` = `prolog_line(Line)` and `Line` is neither a variable nor an integer		`type_error(integer, Line)`

Portability

GNU Prolog predicate.

7.8 Predicate information

7.8.1 current_predicate/1

7.8.2 predicate_property/2

7.8.1 `current_predicate/1`

7.8.2 `predicate_property/2`