X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Flib%2Fstd%2FPrelST.lhs;h=8cf8f372fba61af7cf02e4524cce88af7bf3acaf;hb=2e1d81190f5d80b1431691cc4141ca2c1719ff66;hp=a3a45a3c9390bcb025abdce405dcbcc2b021df01;hpb=449deb80dde91031b86b9cb4fb183696e0139bae;p=ghc-hetmet.git

diff --git a/ghc/lib/std/PrelST.lhs b/ghc/lib/std/PrelST.lhs
index a3a45a3..8cf8f37 100644
--- a/ghc/lib/std/PrelST.lhs
+++ b/ghc/lib/std/PrelST.lhs
@@ -1,6 +1,9 @@
+% ------------------------------------------------------------------------------
+% $Id: PrelST.lhs,v 1.21 2001/09/26 15:12:37 simonpj Exp $
 %
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The University of Glasgow, 1992-2000
 %
+
 \section[PrelST]{The @ST@ monad}
 
 \begin{code}
@@ -8,9 +11,11 @@
 
 module PrelST where
 
-import Monad
 import PrelBase
-import PrelGHC
+import PrelShow
+import PrelNum
+
+default ()
 \end{code}
 
 %*********************************************************
@@ -23,7 +28,8 @@ The state-transformer monad proper.  By default the monad is strict;
 too many people got bitten by space leaks when it was lazy.
 
 \begin{code}
-newtype ST s a = ST (State# s -> (# State# s, a #))
+newtype ST s a = ST (STRep s a)
+type STRep s a = State# s -> (# State# s, a #)
 
 instance Functor (ST s) where
     fmap f (ST m) = ST $ \ s ->
@@ -50,13 +56,6 @@ data STret s a = STret (State# s) a
 liftST :: ST s a -> State# s -> STret s a
 liftST (ST m) = \s -> case m s of (# s', r #) -> STret s' r
 
-fixST :: (a -> ST s a) -> ST s a
-fixST k = ST $ \ s ->
-    let ans       = liftST (k r) s
-	STret _ r = ans
-    in
-    case ans of STret s' x -> (# s', x #)
-
 {-# NOINLINE unsafeInterleaveST #-}
 unsafeInterleaveST :: ST s a -> ST s a
 unsafeInterleaveST (ST m) = ST ( \ s ->
@@ -104,10 +103,18 @@ f = let
 All calls to @f@ will share a {\em single} array!  End SLPJ 95/04.
 
 \begin{code}
-{-# NOINLINE runST #-}
+{-# INLINE runST #-}
+-- The INLINE prevents runSTRep getting inlined in *this* module
+-- so that it is still visible when runST is inlined in an importing
+-- module.  Regrettably delicate.  runST is behaving like a wrapper.
 runST :: (forall s. ST s a) -> a
-runST st = 
-  case st of
-	ST m -> case m realWorld# of
-      			(# _, r #) -> r
+runST st = runSTRep (case st of { ST st_rep -> st_rep })
+
+-- I'm only letting runSTRep be inlined right at the end, in particular *after* full laziness
+-- That's what the "INLINE [0]" says.
+-- 		SLPJ Apr 99
+{-# INLINE [0] runSTRep #-}
+runSTRep :: (forall s. STRep s a) -> a
+runSTRep st_rep = case st_rep realWorld# of
+	      		(# _, r #) -> r
 \end{code}