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Pack logtalk -- logtalk-3.77.0/manuals/_sources/refman/predicates/create_category_4.rst.txt |
.. 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 predicate
.. index:: pair: create_category/4; Built-in predicate .. _predicates_create_category_4:
::
create_category(Identifier, Relations, Directives, Clauses)
Creates a new, dynamic category. This predicate is often used as a primitive to implement high-level category creation methods.
Note that, when opting for runtime generated category identifiers, it's possible to run out of identifiers when using a :term:`backend Prolog compiler` with bounded integer support. The portable solution, when creating a large number of dynamic category in long-running applications, is to recycle, whenever possible, the identifiers.
When creating a new dynamic parametric category, access to the object
parameters must use the :ref:methods_parameter_2
built-in execution
context method.
When using Logtalk multi-threading features, predicates calling this built-in predicate may need to be declared synchronized in order to avoid race conditions.
::
create_category(?category_identifier, @list(category_relation)
, @list(category_directive)
, @list(clause)
) - one
| Relations
, Directives
, or Clauses
is a variable:
| instantiation_error
| Identifier
is neither a variable nor a valid category identifier:
| type_error(category_identifier, Identifier)
| Identifier
is already in use:
| permission_error(modify, category, Identifier)
| permission_error(modify, object, Identifier)
| permission_error(modify, protocol, Identifier)
| Relations
is neither a variable nor a proper list:
| type_error(list, Relations)
| Repeated entity relation clause:
| permission_error(repeat, entity_relation, implements/1)
| permission_error(repeat, entity_relation, extends/1)
| permission_error(repeat, entity_relation, complements/1)
| Directives
is neither a variable nor a proper list:
| type_error(list, Directives)
| Clauses
is neither a variable nor a proper list:
| type_error(list, Clauses)
::
| ?- create_category(
tolerances,
[implements(comparing)],
[],
[epsilon(1e-15), (equal(X, Y) :- epsilon(E), abs(X-Y) =< E)]
)
.
.. seealso::
:ref:predicates_abolish_category_1
, :ref:predicates_category_property_2
,
:ref:predicates_current_category_1
,
:ref:predicates_complements_object_2
, :ref:predicates_extends_category_2_3
,
:ref:predicates_imports_category_2_3