mirror of
https://github.com/Mercury-Language/mercury.git
synced 2026-04-18 10:53:40 +00:00
105 lines
2.1 KiB
Mathematica
105 lines
2.1 KiB
Mathematica
%---------------------------------------------------------------------------%
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% vim: ts=4 sw=4 et ft=mercury
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%---------------------------------------------------------------------------%
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:- module syntax_error_event.
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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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:- implementation.
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:- import_module list.
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:- import_module int.
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:- type listint == list(int).
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main(!IO) :-
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data(Data),
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( if queen(Data, Out) then
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print_list(Out, !IO)
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else
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io.write_string("No solution\n", !IO)
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).
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:- pred data(list(int)::out) is det.
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data([1, 2, 3, 4, 5]).
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:- pred queen(list(int)::in, list(int)::out) is nondet.
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queen(Data, Out) :-
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qperm(Data, Out),
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event safe_test(Data, Out),
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safe(Out).
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:- pred qperm(list(T)::in, list(T)::out) is nondet.
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qperm([], []).
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qperm(L, K) :-
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L = [_ | _],
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qdelete(U, L, Z),
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K = [U | V],
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qperm(Z, V).
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:- pred qdelete(T::out, list(T)::in, list(T)::out) is nondet.
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qdelete(A, [A | L], L).
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qdelete(X, [A | Z], [A | R]) :-
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qdelete(X, Z, R).
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:- pred safe(list(int)::in) is semidet.
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safe([]).
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safe([N | L]) :-
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nodiag(N, 1, L),
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event nodiag_succeed(N, L),
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safe(L).
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:- pred nodiag(int::in, int::in, list(int)::in) is semidet.
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nodiag(_, _, []).
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nodiag(B, D, [N | L]) :-
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NmB = N - B,
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BmN = B - N,
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( if D = NmB then
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event nodiag_fail("N - B", B, N, [N | L]),
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fail
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else if D = BmN then
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event nodiag_fail("B - N", B, N, [N | L]),
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fail
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else
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true
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),
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D1 = D + 1,
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nodiag(B, D1, L).
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:- pred print_list(list(int)::in, io::di, io::uo) is det.
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print_list(Xs, !IO) :-
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(
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Xs = [],
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io.write_string("[]\n", !IO)
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;
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Xs = [_ | _],
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io.write_string("[", !IO),
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print_list_2(Xs, !IO),
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io.write_string("]\n", !IO)
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).
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:- pred print_list_2(list(int)::in, io::di, io::uo) is det.
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print_list_2([], !IO).
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print_list_2([X | Xs], !IO) :-
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io.write_int(X, !IO),
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(
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Xs = []
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;
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Xs = [_ | _],
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io.write_string(", ", !IO),
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print_list_2(Xs, !IO)
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).
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