X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=compiler%2Futils%2FDigraph.lhs;h=939dc4956b830fa7f8bb3bfd870c79a3c2f7f4eb;hb=206b4dec78250efef3cd927d64dc6cbc54a16c3d;hp=addab6c30f10420e0908e73b922eacf4a0a89fdf;hpb=ad94d40948668032189ad22a0ad741ac1f645f50;p=ghc-hetmet.git

diff --git a/compiler/utils/Digraph.lhs b/compiler/utils/Digraph.lhs
index addab6c..939dc49 100644
--- a/compiler/utils/Digraph.lhs
+++ b/compiler/utils/Digraph.lhs
@@ -7,7 +7,7 @@
 -- The above warning supression flag is a temporary kludge.
 -- While working on this module you are encouraged to remove it and fix
 -- any warnings in the module. See
---     http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
 -- for details
 
 module Digraph(
@@ -54,7 +54,7 @@ import Data.Maybe
 import Data.Array
 import Data.List
 
-#if __GLASGOW_HASKELL__ > 604
+#if !defined(__GLASGOW_HASKELL__) || __GLASGOW_HASKELL__ > 604
 import Data.Array.ST
 #else
 import Data.Array.ST  hiding ( indices, bounds )
@@ -83,6 +83,16 @@ instance Outputable a => Outputable (SCC a) where
    ppr (CyclicSCC vs) = text "REC" $$ (nest 3 (vcat (map ppr vs)))
 \end{code}
 
+Note [Nodes, keys, vertices]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ * A 'node' is a big blob of client-stuff
+
+ * Each 'node' has a unique (client) 'key', but the latter 
+	is in Ord and has fast comparison
+
+ * Digraph then maps each 'key' to a Vertex (Int) which is
+  	arranged densely in 0.n
+
 \begin{code}
 stronglyConnComp
         :: Ord key