X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Futils%2FDigraph.lhs;h=f4f2b7e3663887fceb4cd4dce4f733fc590d98ec;hb=92e1151179b419ce5d7a144993053ae982e0df5e;hp=cde008ad9a2307490c26ac88c3f47b1c34b8af18;hpb=9ec880fcb29ff038bcc72d78bbe2fd6933566047;p=ghc-hetmet.git

diff --git a/compiler/utils/Digraph.lhs b/compiler/utils/Digraph.lhs
index cde008a..f4f2b7e 100644
--- a/compiler/utils/Digraph.lhs
+++ b/compiler/utils/Digraph.lhs
@@ -3,6 +3,13 @@
 %
 
 \begin{code}
+{-# OPTIONS_GHC -w #-}
+-- 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/WorkingConventions#Warnings
+-- for details
+
 module Digraph(
 
         -- At present the only one with a "nice" external interface
@@ -323,17 +330,17 @@ preArr bnds      = tabulate bnds . preorderF
 ------------------------------------------------------------
 
 \begin{code}
---postorder :: Tree a -> [a]
-postorder (Node a ts) = postorderF ts ++ [a]
+postorder :: Tree a -> [a] -> [a]
+postorder (Node a ts) = postorderF ts . (a :)
 
-postorderF   :: Forest a -> [a]
-postorderF ts = concat (map postorder ts)
+postorderF   :: Forest a -> [a] -> [a]
+postorderF ts = foldr (.) id $ map postorder ts
 
-postOrd      :: Graph -> [Vertex]
-postOrd       = postorderF . dff
+postOrd :: Graph -> [Vertex]
+postOrd g = postorderF (dff g) []
 
-topSort      :: Graph -> [Vertex]
-topSort       = reverse . postOrd
+topSort :: Graph -> [Vertex]
+topSort = reverse . postOrd
 \end{code}