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.. This file is part of Logtalk https://logtalk.org/ SPDX-FileCopyrightText: 1998-2024 Paulo Moura <pmoura@logtalk.org> SPDX-License-Identifier: Apache-2.0
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
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
.. rst-class:: align-right
built-in method
.. index:: pair: term_expansion/2; Built-in method .. _methods_term_expansion_2:
::
term_expansion(Term, Expansion)
Defines an expansion for a term. This predicate, when defined and within
scope, is automatically called by the :ref:methods_expand_term_2
method.
When that is not the case, the expand_term/2 method only uses the
default expansions. Use of this predicate by the expand_term/2 method
may be restricted by changing its default public scope.
The term_expansion/2 predicate may return a list of terms. Returning an empty list effectively suppresses the term.
Term expansion may be also be applied when compiling source files by
defining the object providing access to the term_expansion/2 clauses
as a :term:`hook object`. Clauses for the
term_expansion/2 predicate defined within an object or a category
are never used in the compilation of the object or the category
itself. Moreover, in this context, terms wrapped using the
:ref:control_external_call_1
compiler bypass control
construct are not expanded and any expanded term wrapped in this control
construct will not be further expanded.
Objects and categories implementing this predicate should declare that they implement the :ref:`expanding apis:expanding/0` protocol if no ancestor already declares it. This protocol implementation relation can be declared as either :ref:`protected or private <inheritance_scope>` to restrict the scope of this predicate.
::
term_expansion(+nonvar, -nonvar)
- zero_or_one
term_expansion(+nonvar, -list(nonvar))
- zero_or_one
(none)
::
term_expansion((:- license(default)), (:- license(gplv3)))
.
term_expansion(data(Millimeters), data(Meters))
:- Meters is Millimeters / 1000.
.. seealso::
:ref:methods_expand_goal_2
,
:ref:methods_expand_term_2
,
:ref:methods_goal_expansion_2
,
:ref:predicates_logtalk_load_context_2