.. 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

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.. 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(?callable, -nonvar) - zero_or_more

Errors

| Key is neither a variable nor a callable term: | type_error(callable, Key) | Key is a callable term but not a valid key: | domain_error(logtalk_load_context_key, Key)

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