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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