[project @ 1998-03-20 09:42:30 by sof]

[ghc-hetmet.git] / ghc / lib / std / PrelST.lhs

diff --git a/ghc/lib/std/PrelST.lhs b/ghc/lib/std/PrelST.lhs
index b3b5411..8513a6a 100644 (file)
--- a/ghc/lib/std/PrelST.lhs
+++ b/ghc/lib/std/PrelST.lhs
@@ -27,6 +27,11 @@ newtype ST s a = ST (State# s -> STret s a)
 
 data STret s a = STret (State# s) a
 
+instance Functor (ST s) where
+    map f (ST m) = ST $ \ s ->
+      case (m s) of { STret new_s r ->
+      STret new_s (f r) }
+
 instance Monad (ST s) where
     {-# INLINE return #-}
     {-# INLINE (>>)   #-}