use_module/2

Description

use_module(Module, [Name/Arity, ...])
use_module(Module, [Name/Arity as Alias/Arity, ...])

use_module(Module, [Name//Arity, ...])
use_module(Module, [Name//Arity as Alias//Arity, ...])

use_module(Module, [op(Precedence,Associativity,Operator), ...])

This directive declares that all calls (made from predicates defined in the category or object containing the directive) to the specified predicates (or non-terminals) are to be interpreted as calls to explicitly-qualified module predicates (or non-terminals). Thus, this directive may be used to simplify writing of predicate definitions by allowing the programmer to omit the Module: prefix when using the predicates listed in the directive (as long as the predicate calls do not occur as arguments for non-standard Prolog meta-predicates not declared on the adapter files). It is also possible to include operator declarations in the second argument.

This directive is also used when compiling calls to the database and reflection built-in methods by examining these methods predicate arguments.

It is possible to specify a predicate alias using the notation Name/Arity as Alias/Arity or, in alternative, the notation Name/Arity:Alias/Arity. Aliases may be used either for avoiding conflicts between predicates specified in use_module/2 and uses/2 directives or for giving more meaningful names considering the calling context of the predicates.

Note that this directive differs from the directive with the same name found on some Prolog implementations by requiring the first argument to be a module name (an atom) instead of a file specification. In Logtalk, there’s no mixing between loading a resource and (declaring the) using (of) a resource. As a consequence, this directive doesn’t automatically load the module. Loading the module file is dependent of the used backend Prolog compiler and must be done separately (usually, using a source file directive such as use_module/1 or use_module/2 in the entity file or preferably in the application loader file). Also, note that the name of the module may differ from the name of the module file.

The modules must be loaded prior to the compilation of entities that call the module predicates. This is required in general to allow the compiler to check if the called module predicate is a meta-predicate and retrieve its meta-predicate template to ensure proper call compilation.

Template and modes

use_module(+module_identifier, +predicate_indicator_list)
use_module(+module_identifier, +predicate_indicator_alias_list)

use_module(+module_identifier, +non_terminal_indicator_list)
use_module(+module_identifier, +non_terminal_indicator_alias_list)

use_module(+module_identifier, +operator_list)

Examples

:- use_module(lists, [append/3, member/2]).
:- use_module(store, [data/2]).
:- use_module(user,  [foo/1 as bar/1]).

foo :-
    ...,
    % same as findall(X, lists:member(X, L), A)
    findall(X, member(X, L), A),
    % same as lists:append(A, B, C)
    append(A, B, C),
    % same as assertz(store:data(X, C))
    assertz(data(X, C)),
    % same as retractall(user:foo(_))
    retractall(bar(_)),
    ...

See also

uses/2