[project @ 2005-03-30 16:24:04 by simonmar]

[ghc-hetmet.git] / ghc / compiler / utils / Digraph.lhs

diff --git a/ghc/compiler/utils/Digraph.lhs b/ghc/compiler/utils/Digraph.lhs
index 0eff6da..c49087c 100644 (file)
--- a/ghc/compiler/utils/Digraph.lhs
+++ b/ghc/compiler/utils/Digraph.lhs
@@ -5,7 +5,8 @@ module Digraph(
        stronglyConnComp, stronglyConnCompR, SCC(..), flattenSCC, flattenSCCs,
 
        Graph, Vertex, 
-       graphFromEdges, buildG, transposeG, reverseE, outdegree, indegree,
+       graphFromEdges, graphFromEdges', 
+       buildG, transposeG, reverseE, outdegree, indegree,
 
        Tree(..), Forest,
        showTree, showForest,
@@ -154,12 +155,19 @@ indegree  = outdegree . transposeG
 
 
 \begin{code}
-graphFromEdges
+graphFromEdges 
        :: Ord key
        => [(node, key, [key])]
        -> (Graph, Vertex -> (node, key, [key]))
-graphFromEdges edges
-  = (graph, \v -> vertex_map ! v)
+graphFromEdges edges = 
+  case graphFromEdges' edges of (graph, vertex_fn, _) -> (graph, vertex_fn) 
+
+graphFromEdges'
+       :: Ord key
+       => [(node, key, [key])]
+       -> (Graph, Vertex -> (node, key, [key]), key -> Maybe Vertex)
+graphFromEdges' edges
+  = (graph, \v -> vertex_map ! v, key_vertex)
   where
     max_v                  = length edges - 1
     bounds          = (0,max_v) :: (Vertex, Vertex)