Logtalk reference manual
Predicate directive: meta_predicate/1
Contents > Reference Manual > Directives > meta_predicate/1

## meta_predicate/1

#### Description

    meta_predicate(MetaPredicateTemplate)
    meta_predicate((MetaPredicateTemplate1, MetaPredicateTemplate2, ...))
    meta_predicate([MetaPredicateTemplate1, MetaPredicateTemplate2, ...])

    meta_predicate(Entity::MetaPredicateTemplate)
    meta_predicate((Entity1::MetaPredicateTemplate1, Entity2::MetaPredicateTemplate2, ...))
    meta_predicate([Entity1::MetaPredicateTemplate1, Entity2::MetaPredicateTemplate2, ...])

    meta_predicate(Module:MetaPredicateTemplate)
    meta_predicate((Module1:MetaPredicateTemplate1, Module2:MetaPredicateTemplate2, ...))
    meta_predicate([Module1:MetaPredicateTemplate1, Module2:MetaPredicateTemplate2, ...])

Declares meta-predicates, i.e., predicates that have arguments that will be called as goals. An argument may also be a closure instead of a goal if the meta-predicate uses the `call/N` Logtalk built-in methods to construct and call the actual goal from the closure and the additional arguments.

Meta-arguments which are goals are represented by the integer `0`. Meta-arguments which are closures are represented by a positive integer, `N`, representing the number of additional arguments that will be appended to the closure in order to construct the corresponding meta-call. Normal arguments are represented by the atom `*`. Meta-arguments are always called in the meta-predicate calling context, not in the meta-predicate definition context.

Logtalk allows the use of this directive to override the original meta-predicate directive. This is sometimes necessary when calling Prolog module meta-predicates due to the lack of standardization of the syntax of the meta-predicate templates.

#### Template and modes

    meta_predicate(+meta_predicate_template_term)

    meta_predicate(+object_identifier::+meta_predicate_template_term)
    meta_predicate(+category_identifier::+meta_predicate_template_term)

    meta_predicate(+module_identifier:+meta_predicate_template_term)

#### Examples

    :- meta_predicate(findall(*, 0, *)).

    :- meta_predicate(forall(0, 0)).

    :- meta_predicate(maplist(2, *, *)).