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   SPDX-License-Identifier: Apache-2.0

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   you may not use this file except in compliance with the License.
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.. rst-class:: align-right

**built-in method**

.. index:: pair: retractall/1; Built-in method
.. _methods_retractall_1:

``retractall/1``
================

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

::

   retractall(Head)

Retracts all clauses with a matching head for an object dynamic predicate.

When the predicate indicator for ``Head`` is declared in a
:ref:`directives_uses_2` or :ref:`directives_use_module_2` directive,
the clauses are retracted in the referenced object or module. When the
backend Prolog compiler supports a module system, the predicate argument
can also be module qualified.

This method may be used to retract clauses for predicates that are not
declared dynamic for dynamic objects provided that the predicates are
declared in :term:`this`.

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

::

   retractall(@callable) - one

Errors
------

| ``Head`` is a variable:
|     ``instantiation_error``
| ``Head`` is neither a variable nor a callable term:
|     ``type_error(callable, Head)``
| The predicate indicator of ``Head``, ``Name/Arity``, is that of a private predicate:
|     ``permission_error(modify, private_predicate, Name/Arity)``
| The predicate indicator of ``Head``, ``Name/Arity``, is that of a protected predicate:
|     ``permission_error(modify, protected_predicate, Name/Arity)``
| The predicate indicator of ``Head``, ``Name/Arity``, is that of a static predicate:
|     ``permission_error(modify, static_predicate, Name/Arity)``
| The predicate indicator of ``Head``, ``Name/Arity``, is not declared:
|     ``existence_error(predicate_declaration, Name/Arity)``

Examples
--------

| To retract all clauses with a matching head of a dynamic predicate in :term:`this`:
|     ``retractall(Head)``
| To retract all clauses with a matching head of a public or protected dynamic predicate in :term:`self`:
|     ``::retractall(Head)``
| To retract all clauses with a matching head of a public dynamic predicate in an explicit object:
|     ``Object::retractall(Head)``

.. seealso::

   :ref:`methods_abolish_1`,
   :ref:`methods_asserta_1`,
   :ref:`methods_assertz_1`,
   :ref:`methods_clause_2`,
   :ref:`methods_retract_1`,
   :ref:`directives_dynamic_0`,
   :ref:`directives_dynamic_1`,
   :ref:`directives_uses_2`,
   :ref:`directives_use_module_2`
