[project @ 2001-05-22 15:06:47 by simonmar]

[ghc-hetmet.git] / ghc / lib / std / PrelIO.hsc

diff --git a/ghc/lib/std/PrelIO.hsc b/ghc/lib/std/PrelIO.hsc
index 4eeaad1..90c8b80 100644 (file)
--- a/ghc/lib/std/PrelIO.hsc
+++ b/ghc/lib/std/PrelIO.hsc
@@ -3,7 +3,7 @@
 #undef DEBUG_DUMP
 
 -- -----------------------------------------------------------------------------
--- $Id: PrelIO.hsc,v 1.2 2001/05/21 14:05:04 simonmar Exp $
+-- $Id: PrelIO.hsc,v 1.3 2001/05/22 15:06:47 simonmar Exp $
 --
 -- (c) The University of Glasgow, 1992-2001
 --
@@ -36,7 +36,7 @@ import PrelHandle     -- much of the real stuff is in here
 import PrelMaybe
 import PrelReal
 import PrelNum
-import PrelRead         ( Read(..), readIO )
+import PrelRead
 import PrelShow
 import PrelMaybe       ( Maybe(..) )
 import PrelPtr
@@ -93,6 +93,20 @@ readLn          =  do l <- getLine
                       r <- readIO l
                       return r
 
+  -- raises an exception instead of an error
+readIO          :: Read a => String -> IO a
+readIO s        =  case (do { (x,t) <- reads s ;
+                             ("","") <- lex t ;
+                              return x }) of
+#ifndef NEW_READS_REP
+                       [x]    -> return x
+                       []     -> ioError (userError "Prelude.readIO: no parse")
+                       _      -> ioError (userError "Prelude.readIO: ambiguous parse")
+#else
+                        Just x -> return x
+                        Nothing  -> ioError (userError "Prelude.readIO: no parse")
+#endif
+
 -- ---------------------------------------------------------------------------
 -- Simple input operations