.. 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: logtalk_load_context/2; Built-in predicate .. _predicates_logtalk_load_context_2:

logtalk_load_context/2

Description

::

logtalk_load_context(Key, Value)

Provides access to the Logtalk compilation/loading context. The following keys are currently supported:

• entity_identifier - identifier of the entity being compiled if any
• entity_prefix - internal prefix for the entity compiled code
• entity_type - returns the value module when compiling a module as an object
• entity_relation - returns the entity relations as declared in the entity opening directive
• source - full path of the source file being compiled
• file - the actual file being compiled, different from source only when processing an include/1 directive
• basename - source file basename
• directory - source file directory
• stream - input stream being used to read source file terms
• target - the full path of the intermediate Prolog file
• flags - the list of the explicit flags used for the compilation of the source file
• term - the source file term being compiled
• term_position - the position of the term being compiled (StartLine-EndLine)
• variables - the variables of the term being compiled ([Variable1, ...])
• variable_names - the variable names of the term being compiled ([Name1=Variable1, ...])
• variable_names(Term) - the variable names of the term being compiled ([Name1=Variable1, ...])
• singletons - the singleton variables of the term being compiled ([Name1=Variable1, ...])
• singletons(Term) - the singleton variables of the term being compiled ([Name1=Variable1, ...])
• parameter_variables - list of parameter variable names and positions ([Name1-Position1, ...]) For the entity_relation key, the possible values are:
• extends_protocol(Protocol, ParentProtocol, Scope)
• implements_protocol(ObjectOrCategory, Protocol, Scope)
• extends_category(Category, ParentCategory, Scope)
• imports_category(Object, Category, Scope)
• extends_object(Prototype, Parent, Scope)
• instantiates_class(Instance, Class, Scope)
• specializes_class(Class, Superclass, Scope)
• complements_object(Category, Object) Calling this predicate with the parameter_variables key only succeeds when compiling a parametric entity containing parameter variables.

  This predicate is usually called by the :ref:methods_term_expansion_2 and :ref:methods_goal_expansion_2 methods. It can also be called directly from :ref:directives_initialization_1 directives in a source file. Note that the entity keys are only available when compiling an entity term or from an object initialization/1 directive.

  .. warning::

  The term_position key is only supported in :term:`backend Prolog compilers <backend Prolog compiler>` that provide access to the start and end lines of a read term. When such support is not available, the value -1 is returned for both the start and the end lines.

  Variables in the values of the term, variables, variable_names, and singletons keys are not shared with, respectively, the term and goal arguments of the term_expansion/2 and goal_expansion/2 methods. Use instead the variable_names(Term) and singletons(Term) keys.

Modes and number of proofs

::

logtalk_load_context(?atom, -nonvar) - zero_or_more

Errors

(none)

Examples

::

% expand source file terms only if they are entity terms term_expansion(Term, ExpandedTerms) :- logtalk_load_context(entity_identifier, _), ....

% expand source file term while accessing its variable names term_expansion(Term, ExpandedTerms) :- logtalk_load_context(variable_names(Term), VariableNames), ....

% define a library alias based on the source directory :- initialization(( logtalk_load_context(directory, Directory), assertz(logtalk_library_path(my_app, Directory)) )).

.. seealso::

:ref:methods_term_expansion_2, :ref:methods_goal_expansion_2, :ref:directives_initialization_1