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:- module ho5.
:- interface.
:- import_module io.

:- pred main(io__state::di, io__state::uo) is cc_multi.

:- implementation.
:- import_module exception.

main -->
    { try(p(1), R1) },
    io__write(R1),
    io__nl,
    { try(p(2), R2) },
    io__write(R2),
    io__nl.

:- pred p(int::in, int::out) is det.

p --> q, r.

:- pred q(int::in, int::out) is det.

q(_, 0).

:- pred r(int::in, int::out) is det.

r(M, N) :-
    (
        M = 0
    ->
        throw(zero)
    ;
        N = 0
    ).

:- func zero(int) = string.

zero(_) = "zero".