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.. rst-class:: align-right

**built-in predicate**

.. index:: pair: threaded_engine_fetch/1; Built-in predicate
.. _predicates_threaded_engine_fetch_1:

``threaded_engine_fetch/1``
===========================

Description
-----------

::

   threaded_engine_fetch(Term)

Fetches a term from the engine term queue. Blocks until a term is
available. Fails if not called from within an engine.

.. note::

   This predicate requires a :term:`backend Prolog compiler` providing
   compatible multi-threading primitives. The value of the read-only
   :ref:`engines <flag_engines>` flag is set to ``supported`` when that
   is the case.

Modes and number of proofs
--------------------------

::

   threaded_engine_fetch(?term) - zero_or_one

Errors
------

(none)

Examples
--------

::

   % fetch a term from the engine term queue:
   ..., threaded_engine_fetch(Term), ...

.. seealso::

   :ref:`predicates_threaded_engine_post_2`
