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62 lines
1.7 KiB
Mathematica
62 lines
1.7 KiB
Mathematica
%---------------------------------------------------------------------------%
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% vim: ts=4 sw=4 et ft=mercury
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%---------------------------------------------------------------------------%
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%
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% Test error messages with problems that arise trying to taking the address
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% of multi-moded predicates.
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:- module multimode_addr_problems.
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:- interface.
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:- import_module io.
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:- pred main(io::di, io::uo) is cc_multi.
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%---------------------------------------------------------------------------%
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%---------------------------------------------------------------------------%
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:- implementation.
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:- import_module int.
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:- import_module list.
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%---------------------------------------------------------------------------%
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main(!IO) :-
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% The compiler can't choose which mode of absolute to use.
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Abs = absolute,
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Abs(3, X),
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io.write_int(X, !IO),
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io.nl(!IO).
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:- pred absolute(int, int).
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:- mode absolute(in, out) is det.
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:- mode absolute(out, in) is multi.
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:- pragma promise_equivalent_clauses(absolute/2).
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absolute(X::in, Y::out) :-
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Y = ( if X < 0 then -X else X).
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absolute(X::out, Y::in) :-
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( X = Y
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; X = -Y
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).
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:- func my_foldl(func(L, A) = A, list(L), A) = A.
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:- mode my_foldl(in(func(in, in) = out is det), in, in) = out is det.
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my_foldl(F, L, A0) = A :-
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% None of the modes of f2p are usable.
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% XXX the error message without this explicit unification is confusing.
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P = f2p(F),
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list.foldl(P, L, A0, A).
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:- pred f2p(func(L, A) = A, L, A, A).
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:- mode f2p(in(func(in, di) = uo is det), in, di, uo) is det.
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% :- mode f2p(in(func(in, in) = out is det), in, in, out) is det.
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:- mode f2p(in(func(in, in) = out is semidet), in, in, out) is semidet.
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f2p(F, L, A0, A) :-
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F(L, A0) = A.
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