X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Data%2FGraph.hs;h=6627f0476ac4591c16016c15882ab3810943ca23;hb=793cc56fbad9da3087e0b26800aec46687ce82dd;hp=12b3a013f560e5f5f4bb1c2ef4f6ab4ef6a23165;hpb=0b07d2ffaf434e9cc0bc08556f5d86b032eb5ac8;p=haskell-directory.git

diff --git a/Data/Graph.hs b/Data/Graph.hs
index 12b3a01..6627f04 100644
--- a/Data/Graph.hs
+++ b/Data/Graph.hs
@@ -6,7 +6,7 @@
 -- 
 -- Maintainer  :  libraries@haskell.org
 -- Stability   :  experimental
--- Portability :  non-portable (requires non-portable module ST)
+-- Portability :  non-portable (uses Control.Monad.ST)
 --
 -- A version of the graph algorithms described in:
 --
@@ -28,7 +28,7 @@ module Data.Graph(
 
 	-- ** Building graphs
 
-	graphFromEdges, buildG, transposeG,
+	graphFromEdges, graphFromEdges', buildG, transposeG,
 	-- reverseE,
 
 	-- ** Graph properties
@@ -43,7 +43,7 @@ module Data.Graph(
 	components,
 	scc,
 	bcc,
-	-- back, cross, forward,
+	-- tree, back, cross, forward,
 	reachable, path,
 
 	module Data.Tree
@@ -60,6 +60,10 @@ import Data.Maybe
 import Data.Array
 import Data.List
 
+#ifdef __HADDOCK__
+import Prelude
+#endif
+
 -------------------------------------------------------------------------
 --									-
 --	External interface
@@ -117,7 +121,7 @@ stronglyConnCompR [] = []  -- added to avoid creating empty array in graphFromEd
 stronglyConnCompR edges0
   = map decode forest
   where
-    (graph, vertex_fn) = graphFromEdges edges0
+    (graph, vertex_fn,_) = graphFromEdges edges0
     forest	       = scc graph
     decode (Node v []) | mentions_itself v = CyclicSCC [vertex_fn v]
 		       | otherwise	   = AcyclicSCC (vertex_fn v)
@@ -175,6 +179,16 @@ outdegree  = mapT numEdges
 indegree :: Graph -> Table Int
 indegree  = outdegree . transposeG
 
+-- | Identical to 'graphFromEdges', except that the return value
+-- does not include the function which maps keys to vertices.  This
+-- version of 'graphFromEdges' is for backwards compatibility.
+graphFromEdges'
+	:: Ord key
+	=> [(node, key, [key])]
+	-> (Graph, Vertex -> (node, key, [key]))
+graphFromEdges' x = (a,b) where
+    (a,b,_) = graphFromEdges x
+
 -- | Build a graph from a list of nodes uniquely identified by keys,
 -- with a list of keys of nodes this node should have edges to.
 -- The out-list may contain keys that don't correspond to
@@ -182,9 +196,9 @@ indegree  = outdegree . transposeG
 graphFromEdges
 	:: Ord key
 	=> [(node, key, [key])]
-	-> (Graph, Vertex -> (node, key, [key]))
+	-> (Graph, Vertex -> (node, key, [key]), key -> Maybe Vertex)
 graphFromEdges edges0
-  = (graph, \v -> vertex_map ! v)
+  = (graph, \v -> vertex_map ! v, key_vertex)
   where
     max_v      	    = length edges0 - 1
     bounds0         = (0,max_v) :: (Vertex, Vertex)
@@ -321,6 +335,10 @@ scc g = dfs g (reverse (postOrd (transposeG g)))
 -- Algorithm 5: Classifying edges
 ------------------------------------------------------------
 
+tree              :: Bounds -> Forest Vertex -> Graph
+tree bnds ts       = buildG bnds (concat (map flat ts))
+ where flat (Node v ts) = [ (v, w) | Node w _us <- ts ] ++ concat (map flat ts)
+
 back              :: Graph -> Table Int -> Graph
 back g post        = mapT select g
  where select v ws = [ w | w <- ws, post!v < post!w ]