mercury_lib.m

% This source file is hereby placed in the public domain.  -fjh (the author).

%-----------------------------------------------------------------------------%
:- module mercury_lib.
:- interface.

    % A Mercury predicate with multiple modes.
    %
:- pred foo(int).
:- mode foo(in) is semidet.
:- mode foo(out) is multi.

    % A Mercury function with multiple modes.
    %
:- func bar(int) = int.
:- mode bar(in) = out is det.
:- mode bar(out) = in is det.
:- mode bar(in) = in is semidet.

    % A semidet (i.e. partial) Mercury function.
:- func baz(int) = int.
:- mode baz(in) = out is semidet.

%-----------------------------------------------------------------------------%
%-----------------------------------------------------------------------------%

:- implementation.

:- import_module int.
:- import_module list.
:- import_module solutions.

% well, this is just a silly example...
foo(42).
foo(53).
foo(197).

bar(X) = X + 1.

baz(1) = 9.
baz(2) = 16.
baz(3) = 27.

%-----------------------------------------------------------------------------%

% The following code provides provides access to the Mercury predicate foo
% from Java code.

:- pragma foreign_export("Java", foo(in), "foo_test").

:- pragma foreign_export("Java", bar(in) = out, "bar").
:- pragma foreign_export("Java", bar(in) = in,  "bar_test").
:- pragma foreign_export("Java", bar(out) = in, "bar_inverse").

:- pragma foreign_export("Java", baz(in) = out, "baz").

    % The nondet mode of `foo' cannot be exported directly with the
    % Mercury/Java interface.  To get all solutions, must define a predicate
    % which returns all the solutions of foo, and export it to Java.  We give
    % it the name foo_list() in Java.
:- pred all_foos(list(int)::out) is det.
:- pragma foreign_export("Java", all_foos(out), "foo_list").
all_foos(L) :- solutions((pred(X::out) is multi :- foo(X)), L).

    % If we just want one solution, and don't care which one, then we can
    % export a `cc_multi' (committed-choice nondeterminism) version of `foo'.
    % We give it the name one_foo().
:- pred cc_foo(int::out) is cc_multi.
:- pragma foreign_export("Java", cc_foo(out), "one_foo").
cc_foo(X) :- foo(X).

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