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.. rst-class:: align-right

built-in method

.. index:: pair: phrase/3; Built-in method .. _methods_phrase_3:

phrase/3

Description

::

phrase(GrammarRuleBody, Input, Rest) phrase(::GrammarRuleBody, Input, Rest) phrase(Object::GrammarRuleBody, Input, Rest)

True when the GrammarRuleBody grammar rule body can be applied to the Input-Rest difference list of tokens. In the most common case, GrammarRuleBody is a non-terminal defined by a grammar rule. This built-in method is declared private and thus cannot be used as a message to an object. When using a :term:`backend Prolog compiler` supporting a module system, calls in the format phrase(Module:GrammarRuleBody, Input, Rest) may also be used.

This method is opaque to cuts in the first argument. When the first argument is sufficiently instantiated at compile time, the method call is compiled in order to eliminate the implicit overheads of converting the grammar rule body into a goal and meta-calling it. For performance reasons, the second and third arguments are only type-checked at compile time.

Meta-predicate template

::

phrase(2, *, *)

Modes and number of proofs

::

phrase(+callable, ?list, ?list) - zero_or_more

Errors

| GrammarRuleBody is a variable: | instantiation_error | GrammarRuleBody is neither a variable nor a callable term: | type_error(callable, GrammarRuleBody)

Examples

| To parse a list of tokens using a local non-terminal: | phrase(NonTerminal, Input, Rest) | To parse a list of tokens using a non-terminal within the scope of :term:self: | phrase(::NonTerminal, Input, Rest) | To parse a list of tokens using a public non-terminal of an explicit object: | phrase(Object::NonTerminal, Input, Rest)

.. seealso::

:ref:methods_call_1, :ref:methods_phrase_2, :ref:methods_phrase_3