188 lines
4.8 KiB
Prolog
188 lines
4.8 KiB
Prolog
% File : dgraphs.yap
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% Author : Vitor Santos Costa
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% Updated: 2006
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% Purpose: Directed Graph Processing Utilities.
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:- module( undgraphs,
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[
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undgraph_new/1,
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undgraph_add_edge/4,
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undgraph_add_edges/3,
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undgraph_add_vertices/3,
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undgraph_del_edge/4,
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undgraph_del_edges/3,
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undgraph_del_vertex/3,
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undgraph_del_vertices/3,
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undgraph_edge/3,
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undgraph_edges/2,
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undgraph_neighbors/3,
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undgraph_neighbours/3,
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undgraph_complement/2,
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undgraph_components/2,
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dgraph_to_undgraph/2,
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undgraph_min_tree/2]).
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:- reexport( library(dgraphs),
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[
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dgraph_new/1 as undgraph_new,
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dgraph_add_vertex/3 as undgraph_add_vertex,
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dgraph_vertices/2 as undgraph_vertices,
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dgraph_complement/2 as undgraph_complement,
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dgraph_symmetric_closure/2 as dgraph_to_undgraph,
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dgraph_edge/3 as undgraph_edge,
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dgraph_reachable/3 as undgraph_reachable
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]).
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:- use_module( library(dgraphs),
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[
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dgraph_add_edge/4,
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dgraph_add_edges/3,
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dgraph_add_vertices/3,
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dgraph_del_edge/4,
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dgraph_del_edges/3,
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dgraph_del_vertex/3,
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dgraph_del_vertices/3,
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dgraph_edges/2,
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dgraph_neighbors/3,
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dgraph_neighbours/3]).
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:- use_module(library(wundgraphs), [
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undgraph_to_wundgraph/2,
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wundgraph_min_tree/3,
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wundgraph_max_tree/3,
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wundgraph_to_undgraph/2]).
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:- use_module(library(ordsets),
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[ ord_del_element/3,
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ord_union/3,
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ord_subtract/3]).
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:- use_module(library(rbtrees),
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[ rb_delete/4,
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rb_insert/4,
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rb_in/3,
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rb_partial_map/4
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]).
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undgraph_add_edge(Vs0,V1,V2,Vs2) :-
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dgraphs:dgraph_new_edge(V1,V2,Vs0,Vs1),
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dgraphs:dgraph_new_edge(V2,V1,Vs1,Vs2).
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undgraph_add_edges(G0, Edges, GF) :-
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dup_edges(Edges, DupEdges),
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dgraph_add_edges(G0, DupEdges, GF).
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dup_edges([],[]).
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dup_edges([E1-E2|Edges], [E1-E2,E2-E1|DupEdges]) :-
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dup_edges(Edges, DupEdges).
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undgraph_add_vertices(G, [], G).
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undgraph_add_vertices(G0, [V|Vs], GF) :-
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dgraph_add_vertex(G0, V, GI),
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undgraph_add_vertices(GI, Vs, GF).
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undgraph_edges(Vs,Edges) :-
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dgraph_edges(Vs,DupEdges),
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remove_dups(DupEdges,Edges).
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remove_dups([],[]).
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remove_dups([V1-V2|DupEdges],NEdges) :- V1 @< V2, !,
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NEdges = [V1-V2|Edges],
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remove_dups(DupEdges,Edges).
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remove_dups([_|DupEdges],Edges) :-
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remove_dups(DupEdges,Edges).
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undgraph_neighbours(V,Vertices,Children) :-
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dgraph_neighbours(V,Vertices,Children0),
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(
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ord_del_element(Children0,V,Children)
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->
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true
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;
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Children = Children0
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).
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undgraph_neighbors(V,Vertices,Children) :-
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dgraph_neighbors(V,Vertices,Children0),
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(
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ord_del_element(Children0,V,Children)
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->
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true
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;
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Children = Children0
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).
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undgraph_del_edge(Vs0,V1,V2,VsF) :-
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dgraph_del_edge(Vs0,V1,V2,Vs1),
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dgraph_del_edge(Vs1,V2,V1,VsF).
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undgraph_del_edges(G0, Edges, GF) :-
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dup_edges(Edges,DupEdges),
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dgraph_del_edges(G0, DupEdges, GF).
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undgraph_del_vertex(Vs0, V, Vsf) :-
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rb_delete(Vs0, V, BackEdges, Vsi),
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(
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ord_del_element(BackEdges,V,RealBackEdges)
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->
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true
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;
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BackEdges = RealBackEdges
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),
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rb_partial_map(Vsi, RealBackEdges, del_edge(V), Vsf).
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undgraph_del_vertices(G0, Vs, GF) :-
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sort(Vs,SortedVs),
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delete_all(SortedVs, [], BackEdges, G0, GI),
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ord_subtract(BackEdges, SortedVs, TrueBackEdges),
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delete_remaining_edges(SortedVs, TrueBackEdges, GI, GF).
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% it would be nice to be able to delete a set of elements from an RB tree
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% but I don't how to do it yet.
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delete_all([], BackEdges, BackEdges) --> [].
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delete_all([V|Vs], BackEdges0, BackEdgesF, Vs0,Vsf) :-
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rb_delete(Vs0, V, NewEdges, Vsi),
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ord_union(NewEdges,BackEdges0,BackEdgesI),
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delete_all(Vs, BackEdgesI ,BackEdgesF, Vsi,Vsf).
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delete_remaining_edges(SortedVs, TrueBackEdges, Vs0,Vsf) :-
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rb_partial_map(Vs0, TrueBackEdges, del_edges(SortedVs), Vsf).
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del_edges(ToRemove,E0,E) :-
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ord_subtract(E0,ToRemove,E).
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del_edge(ToRemove,E0,E) :-
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ord_del_element(E0,ToRemove,E).
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undgraph_min_tree(G, T) :-
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undgraph_to_wundgraph(G, WG),
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wundgraph_min_tree(WG, WT, _),
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wundgraph_to_undgraph(WT, T).
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undgraph_max_tree(G, T) :-
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undgraph_to_wundgraph(G, WG),
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wundgraph_max_tree(WG, WT, _),
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wundgraph_to_undgraph(WT, T).
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undgraph_components(Graph,[Map|Gs]) :-
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pick_node(Graph,Node,Children,Graph1), !,
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undgraph_new(Map0),
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rb_insert(Map0, Node, Children, Map1),
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expand_component(Children, Map1, Map, Graph1, NGraph),
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undgraph_components(NGraph,Gs).
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undgraph_components(_,[]).
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expand_component([], Map, Map, Graph, Graph).
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expand_component([C|Children], Map1, Map, Graph1, NGraph) :-
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rb_delete(Graph1, C, Edges, Graph2), !,
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rb_insert(Map1, C, Edges, Map2),
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expand_component(Children, Map2, Map3, Graph2, Graph3),
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expand_component(Edges, Map3, Map, Graph3, NGraph).
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expand_component([_|Children], Map1, Map, Graph1, NGraph) :-
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expand_component(Children, Map1, Map, Graph1, NGraph).
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pick_node(Graph,Node,Children,Graph1) :-
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rb_in(Node,Children,Graph), !,
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rb_delete(Graph, Node, Graph1).
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