Use OPTIONS rather than OPTIONS_GHC for pragmas

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

diff --git a/compiler/utils/Digraph.lhs b/compiler/utils/Digraph.lhs
index cde008a..addab6c 100644 (file)
--- a/compiler/utils/Digraph.lhs
+++ b/compiler/utils/Digraph.lhs
@@ -3,6 +3,13 @@
 %
 
 \begin{code}
+{-# OPTIONS -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/CodingStyle#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}