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% vim: ts=4 sw=4 et ft=mercury
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:- module any_mode.

:- interface.

:- solver type foo
    where representation is int,
          ground         is ground,
          any            is ground,
          equality       is eq_foo.

:- pred p(foo::(any >> ground)) is semidet.
:- pred q(foo::in) is semidet.

:- implementation.

p(X) :- q(X).

q(foo(123)).

:- pred init_foo(foo::out(any)) is det.
init_foo(foo(42)).

:- func foo(int::in) = (foo::out(any)) is det.
:- pragma promise_pure(foo/1).
foo(N) = X :-
    impure X = 'representation to any foo/0'(N).

:- pred eq_foo(foo::in(any), foo::in(any)) is semidet.
:- pragma promise_pure(eq_foo/2).
eq_foo(X, Y) :-
    impure RX = 'representation of any foo/0'(X),
    impure RY = 'representation of any foo/0'(Y),
    RX = RY.