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:- module graph.

:- interface.
:- import_module string.
:- import_module list.

:- type graph == list({ string, string, string }).

:- pred contains(graph, string).
:- mode contains(in, in) is semidet.
:- mode contains(in, out) is nondet.

:- pred contains(graph, string, string, string).
:- mode contains(in, in, in, in) is semidet.
:- mode contains(in, in, in, out) is nondet.
:- mode contains(in, in, out, in) is nondet.
:- mode contains(in, out, in, in) is nondet.
:- mode contains(in, in, out, out) is nondet.
:- mode contains(in, out, in, out) is nondet.
:- mode contains(in, out, out, in) is nondet.
:- mode contains(in, out, out, out) is nondet.

:- implementation.

contains(G, S) :-
	contains(G, S, _, _);
	contains(G, _, S, _);
	contains(G, _, _, S).

contains([ Head | Tail ], S, P, O) :-
	Head = { S, P, O };
	contains(Tail, S, P, O).