For procedures, the local-declaration is normally redundant because local visibility is the default. However, it might be necessary to explicitly declare a procedure as local to resolve a name conflict when an imported module exports a procedure of the same name.
Local declarations should be placed at the beginning of a module text. They must occur before the first reference to the declared prodecure:
A procedure can have four kinds of visibility in a given module: local, exported, imported or reexported. A local-declaration is silently ignored if the procedure has already been exported before. If a procedure of the given name has already been imported or reexported, the local-declaration raises an error 94. If there is one or more imported modules which export a procedure of the same name, these all get hidden silently by the local declaration.
A local procedure can only be called from within the module where it is defined, even when explicit module qualification via :/2 is used.
Local Initialization and Finalization
The local initialization declaration is used to specify an initialization goal. All initialization goals which occur within a compilation unit (file or module), will be executed just after this compilation unit has been loaded by the system.
A finalization goal will be executed just before the module containing the declaration gets erased. This can happen either explicitly through erase_module/1, or implicitly when the module gets recompiled or when ECLiPSe exits. Finalisation goals should not do any I/O because in the case of an embedded ECLiPSe, I/O may no longer be available at finalisation time.
Other Local Items
All other local declarations also have an effect only in the module where they occur. Some of them have corresponding export-variants.
The local/1 primitive can not only occur as a directive but can also be called at runtime.
Duplicate local declarations are accepted silently.
% Normally, local declarations for predicates are redundant: :- module(m). :- local p/1. % can be omitted since the default is local p(99). % Redefining a built-in predicate: :- module(m) :- local writeln/1. % stop writeln/1 from being imported main :- writeln(hello). % local-declaration must be before this use! writeln(X) :- % the local version printf("I don't like the normal writeln/1 predicate: %w%n",[X]). % Redefining an imported predicate: :- module(m) :- lib(lists). % module 'lists' defines a predicate subtract/3 :- local subtract/3. % stop subtract/3 being imported from 'lists' decr(N, N1) :- subtract(N,1,N1). % local-declaration must be before this use! subtract(X,Y,Z) :- % the local version of subtract/3 Z is X-Y. % Other local declarations: :- local op(500, xfx, before), struct(book(author,title,publisher)). :- local initialization(writeln("I am being initialized!")). % Error cases: :- local P. (Error 4). :- local p/a. (Error 5). :- (import p/0 from m), local(p/0) (Error 94).