[project @ 2004-11-13 14:37:18 by panne]

[ghc-base.git] / GHC / IOBase.lhs

diff --git a/GHC/IOBase.lhs b/GHC/IOBase.lhs
index 6fa596a..8700128 100644 (file)
--- a/GHC/IOBase.lhs
+++ b/GHC/IOBase.lhs
@@ -122,6 +122,12 @@ stToIO (ST m) = IO m
 ioToST       :: IO a -> ST RealWorld a
 ioToST (IO m) = (ST m)
 
+-- This relies on IO and ST having the same representation modulo the
+-- constraint on the type of the state
+--
+unsafeIOToST        :: IO a -> ST s a
+unsafeIOToST (IO io) = ST $ \ s -> (unsafeCoerce# io) s
+
 -- ---------------------------------------------------------------------------
 -- Unsafe IO operations
 
@@ -260,6 +266,15 @@ instance Eq (MVar a) where
 -- enough information to identify the handle for debugging.  A handle is
 -- equal according to '==' only to itself; no attempt
 -- is made to compare the internal state of different handles for equality.
+--
+-- GHC note: a 'Handle' will be automatically closed when the garbage
+-- collector detects that it has become unreferenced by the program.
+-- However, relying on this behaviour is not generally recommended:
+-- the garbage collector is unpredictable.  If possible, use explicit
+-- an explicit 'hClose' to close 'Handle's when they are no longer
+-- required.  GHC does not currently attempt to free up file
+-- descriptors when they have run out, it is your responsibility to
+-- ensure that this doesn't happen.
 
 data Handle 
   = FileHandle                         -- A normal handle to a file