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Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

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.. rst-class:: align-right

built-in method

.. index:: pair: call//1-N; Built-in method .. _methods_call_1:

call//1-N

Description

::

call(Closure) call(Closure, Arg1, ...) call(Object::Closure, Arg1, ...) call(::Closure, Arg1, ...) call(^^Closure, Arg1, ...) ...

This non-terminal takes a :term:closure and is processed by appending the two implicit grammar rule arguments to the arguments of the closure. This built-in non-terminal is interpreted as a private non-terminal and thus cannot be used as a message to an object.

Using this non-terminal is recommended when calling a predicate whose last two arguments are the two implicit grammar rule arguments to avoid hard-coding assumptions about how grammar rules are compiled into clauses. Note that the compiler ensures zero overhead when using this non-terminal with a bound argument at compile time. To call a predicate with a different argument order, use a :term:`lambda expression` or define a :term:`predicate alias`. For example:

::

square --> call([Number, Double]>>(Double is Number*Number)).

When using a :term:`backend Prolog compiler` supporting a module system, calls in the format call(Module:Closure) may also be used.

Meta-non-terminal template

::

call(0) call(1, *) call(2, *, *) ...

Modes and number of proofs

::

call(+callable) - zero_or_more call(+callable, ?term) - zero_or_more call(+callable, ?term, ?term) - zero_or_more ...

Errors

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

Examples

| Calls a goal, constructed by appending the two implicit grammar rule arguments to the closure, in in the context of the object or category containing the call: | call(Closure) | To make a super call, constructed by appending the two implicit grammar rule arguments to the closure: | call(^^Closure) | To send a goal, constructed by appending the two implicit grammar rule arguments to the closure, as a message to :term:self: | call(::Closure) | To send a goal, constructed by appending the two implicit grammar rule arguments to the closure, as a message to an explicit object: | call(Object::Closure)

.. seealso::

:ref:methods_eos_0, :ref:methods_phrase_1, :ref:methods_phrase_2, :ref:methods_phrase_3