Predicate information

6.8

Predicate information

6.8.1 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 6.22.1). 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 6.22.1) representation_error(max_arity)

Portability

ISO predicate.

6.8.2 predicate_property/2

Templates

: predicate_property(?predicate_indicator, ?predicate_property)

Description

predicate_property(Pred, Property) succeeds if current_predicate(Pred) succeeds (section 6.8.1) and if Property unifies with one of the properties of the procedure. 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 6.22.1) 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.

Copyright (C) 1999,2000 Daniel Diaz

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