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(*
* This view combinator converts a multigraph into a simple graph.
*
* -- Allen
*)
signature SIMPLE_GRAPH =
sig
val simple_graph :
(Graph.node_id * Graph.node_id * 'e list -> 'e) ->
('n,'e,'g) Graph.graph -> ('n,'e,'g) Graph.graph
end
structure SimpleGraph =
struct
structure G = Graph
structure S = ListMergeSort
fun simple_graph merge (G.GRAPH G) =
let val sort = S.sort (fn ((i,j,_),(i',j',_)) =>
i > i' orelse i = i' andalso j > j')
fun uniq([],_,_,[],es'') = es''
| uniq([],i,j,[e],es'') = (i,j,e)::es''
| uniq([],i,j,es,es'') = (i,j,merge(i,j,es))::es''
| uniq((i,j,e)::es,_,_,[],es'') = uniq(es,i,j,[e],es'')
| uniq((i,j,e)::es,i',j',es',es'') =
if i = i andalso j = j' then
uniq(es,i',j',e::es',es'')
else (case es' of
[e'] => uniq(es,i,j,[e],(i',j',e')::es'')
| _ => uniq(es,i,j,[e],(i',j',merge(i',j',es'))::es'')
)
fun unique es = uniq(sort es,~1,~1,[],[])
fun out_edges v = unique(#out_edges G v)
fun in_edges v = unique(#in_edges G v)
fun succ v = map #2 (out_edges v)
fun pred v = map #1 (in_edges v)
fun edges() = unique(#edges G ())
in G.GRAPH
{ name = #name G,
graph_info = #graph_info G,
new_id = #new_id G,
add_node = #add_node G,
add_edge = #add_edge G,
remove_node = #remove_node G,
set_in_edges = #set_in_edges G,
set_out_edges = #set_out_edges G,
set_entries = #set_entries G,
set_exits = #set_exits G,
garbage_collect = #garbage_collect G,
nodes = #nodes G,
edges = edges,
order = #order G,
size = #size G,
capacity = #capacity G,
out_edges = out_edges,
in_edges = in_edges,
succ = succ,
pred = pred,
has_edge = #has_edge G,
has_node = #has_node G,
node_info = #node_info G,
entries = #entries G,
exits = #exits G,
entry_edges = #entry_edges G,
exit_edges = #exit_edges G,
forall_nodes = #forall_nodes G,
forall_edges = fn f => app f (edges ())
}
end
end
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