35 lines
810 B
Prolog
35 lines
810 B
Prolog
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:- module(topsort, [topsort/2]).
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:- use_module(library(dgraphs),
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[dgraph_new/1,
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dgraph_add_edges/3,
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dgraph_add_vertices/3,
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dgraph_top_sort/2]).
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/* simple implementation of a topological sorting algorithm */
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/* graph is as Node-[Parents] */
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topsort(Graph0, Sorted) :-
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mkedge_list(Graph0, EdgeList, []),
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mkvertices_list(Graph0, VList, []),
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dgraph_new(DGraph0),
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dgraph_add_vertices(DGraph0, VList, DGraph1),
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dgraph_add_edges(DGraph1, EdgeList, DGraph2),
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dgraph_top_sort(DGraph2, Sorted).
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mkvertices_list([]) --> [].
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mkvertices_list([V-_|More]) --> [V],
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mkvertices_list(More).
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mkedge_list([]) --> [].
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mkedge_list([V-Parents|More]) -->
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add_edges(Parents, V),
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mkedge_list(More).
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add_edges([], _V) --> [].
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add_edges([P|Parents], V) --> [P-V],
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add_edges(Parents, V).
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