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.. rst-class:: align-right

directive

.. index:: pair: meta_non_terminal/1; Directive .. _directives_meta_non_terminal_1:

meta_non_terminal/1

Description

::

meta_non_terminal(Template) meta_non_terminal((Template, ...)) meta_non_terminal([Template, ...])

meta_non_terminal(Entity::Template) meta_non_terminal((Entity::Template, ...)) meta_non_terminal([Entity::Template, ...])

meta_non_terminal(Module:Template) meta_non_terminal((Module:Template, ...)) meta_non_terminal([Module:Template, ...])

Declares meta-non-terminals, i.e., non-terminals that have arguments that will be called as non-terminals (or grammar rule bodies). An argument may also be a :term:closure instead of a goal if the non-terminal uses the :ref:methods_call_1 built-in methods to construct and call the actual non-terminal from the closure and the additional arguments or the :ref:methods_phrase_1 built-in method.

Meta-arguments which are non-terminals 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-non-terminal calling context, not in the meta-non-terminal definition context.

Template and modes

::

meta_non_terminal(+meta_non_terminal_template_term)

meta_non_terminal(+object_identifier::+meta_non_terminal_template_term) meta_non_terminal(+category_identifier::+meta_non_terminal_template_term)

meta_non_terminal(+module_identifier:+meta_non_terminal_template_term)

Examples

::

:- meta_non_terminal(phrase(1, *)). phrase(X, T) --> call(X, T).

.. seealso::

:ref:directives_meta_predicate_1, :ref:methods_predicate_property_2