doc updates in System.IO

[ghc-base.git] / GHC / Exts.hs

diff --git a/GHC/Exts.hs b/GHC/Exts.hs
index bc36771..661f5aa 100644 (file)
--- a/GHC/Exts.hs
+++ b/GHC/Exts.hs
@@ -41,7 +41,10 @@ module GHC.Exts
         lazy, inline,
 
         -- * Transform comprehensions
-        Down(..), groupWith, sortWith, the
+        Down(..), groupWith, sortWith, the,
+
+        -- * Event logging
+        traceEvent
 
        ) where
 
@@ -49,12 +52,14 @@ import Prelude
 
 import GHC.Prim
 import GHC.Base
+import GHC.Magic
 import GHC.Word
 import GHC.Int
-import GHC.Float
+-- import GHC.Float
 import GHC.Ptr
 import Data.String
 import Data.List
+import Foreign.C
 
 -- XXX This should really be in Data.Tuple, where the definitions are
 maxTupleSize :: Int
@@ -92,8 +97,16 @@ groupWith :: Ord b => (a -> b) -> [a] -> [[a]]
 groupWith f xs = build (\c n -> groupByFB c n (\x y -> f x == f y) (sortWith f xs))
 
 groupByFB :: ([a] -> lst -> lst) -> lst -> (a -> a -> Bool) -> [a] -> lst
-groupByFB c n eq xs = groupByFBCore xs
+groupByFB c n eq xs0 = groupByFBCore xs0
   where groupByFBCore [] = n
         groupByFBCore (x:xs) = c (x:ys) (groupByFBCore zs)
             where (ys, zs) = span (eq x) xs
 
+
+-- -----------------------------------------------------------------------------
+-- tracing
+
+traceEvent :: String -> IO ()
+traceEvent msg = do
+  withCString msg $ \(Ptr p) -> IO $ \s ->
+    case traceEvent# p s of s' -> (# s', () #)