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[smlnj] View of /MLRISC/releases/release-110.60/graphs/acyclic-graph.sml
 [smlnj] / MLRISC / releases / release-110.60 / graphs / acyclic-graph.sml

# View of /MLRISC/releases/release-110.60/graphs/acyclic-graph.sml

Thu Nov 9 21:29:12 2006 UTC (12 years, 9 months ago) by blume
File size: 989 byte(s)
`Release 110.60`
```(*
* Acyclic subgraph adaptor.  This takes a linear order of node id
* return a view in which only the edges (and nodes) consistent with
* the linear order is visible.
*
* -- Allen
*)

signature ACYCLIC_SUBGRAPH_VIEW =
sig

(* Acyclic node induced subgraph *)
val acyclic_view : Graph.node_id list ->
('n,'e,'g) Graph.graph ->
('n,'e,'g) Graph.graph
end

structure AcyclicSubgraphView : ACYCLIC_SUBGRAPH_VIEW =
struct

structure G = Graph
structure A = HashArray
structure S = Subgraph_P_View

fun acyclic_view nodes (G as G.GRAPH g) =
let val ord = A.array(#capacity g (),~1)
fun order(i,[]) = ()
| order(i,n::ns) = (A.update(ord,n,i); order(i+1,ns))
val _ = order(0,nodes)
fun node_p i = A.sub(ord,i) >= 0
fun edge_p (i,j) =
let val i = A.sub(ord,i)
in  i >= 0 andalso i < A.sub(ord,j) end
in  S.subgraph_p_view nodes node_p edge_p G
end

end

```