X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=GHC%2FExts.hs;h=661f5aa275934b6bb43909afd65606ef6f69d72c;hb=bad25ed6cb9b939d786e53d3074f0cd4f869af28;hp=f0c2321c224083bd7d9f27047f407833ccdd4f58;hpb=3ce77a0160b7269972b98d81e8db4936047c1df6;p=ghc-base.git

diff --git a/GHC/Exts.hs b/GHC/Exts.hs
index f0c2321..661f5aa 100644
--- a/GHC/Exts.hs
+++ b/GHC/Exts.hs
@@ -15,26 +15,36 @@
 module GHC.Exts
        (
         -- * Representations of some basic types
-        Int(..),Word(..),Float(..),Double(..),Integer(..),Char(..),
-	Ptr(..), FunPtr(..),
+        Int(..),Word(..),Float(..),Double(..),
+        Char(..),
+        Ptr(..), FunPtr(..),
+
+        -- * The maximum tuple size
+        maxTupleSize,
 
         -- * Primitive operations
         module GHC.Prim,
-	shiftL#, shiftRL#, iShiftL#, iShiftRA#, iShiftRL#,
+        shiftL#, shiftRL#, iShiftL#, iShiftRA#, iShiftRL#,
         uncheckedShiftL64#, uncheckedShiftRL64#,
         uncheckedIShiftL64#, uncheckedIShiftRA64#,
 
-	-- * Fusion
-	build, augment,
+        -- * Fusion
+        build, augment,
+
+        -- * Overloaded string literals
+        IsString(..),
+
+        -- * Debugging
+        breakpoint, breakpointCond,
 
-	-- * Overloaded string literals
-	IsString(..),
+        -- * Ids with special behaviour
+        lazy, inline,
 
-	-- * Debugging
-	breakpoint, breakpointCond,
+        -- * Transform comprehensions
+        Down(..), groupWith, sortWith, the,
 
-	-- * Ids with special behaviour
-	lazy, inline,
+        -- * Event logging
+        traceEvent
 
        ) where
 
@@ -42,10 +52,61 @@ import Prelude
 
 import GHC.Prim
 import GHC.Base
+import GHC.Magic
 import GHC.Word
 import GHC.Int
-import GHC.Num
-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
+maxTupleSize = 62
+
+-- | The 'Down' type allows you to reverse sort order conveniently.  A value of type
+-- @'Down' a@ contains a value of type @a@ (represented as @'Down' a@).
+-- If @a@ has an @'Ord'@ instance associated with it then comparing two
+-- values thus wrapped will give you the opposite of their normal sort order.
+-- This is particularly useful when sorting in generalised list comprehensions,
+-- as in: @then sortWith by 'Down' x@
+newtype Down a = Down a deriving (Eq)
+
+instance Ord a => Ord (Down a) where
+    compare (Down x) (Down y) = y `compare` x
+
+-- | 'the' ensures that all the elements of the list are identical
+-- and then returns that unique element
+the :: Eq a => [a] -> a
+the (x:xs)
+  | all (x ==) xs = x
+  | otherwise     = error "GHC.Exts.the: non-identical elements"
+the []            = error "GHC.Exts.the: empty list"
+
+-- | The 'sortWith' function sorts a list of elements using the
+-- user supplied function to project something out of each element
+sortWith :: Ord b => (a -> b) -> [a] -> [a]
+sortWith f = sortBy (\x y -> compare (f x) (f y))
+
+-- | The 'groupWith' function uses the user supplied function which
+-- projects an element out of every list element in order to to first sort the 
+-- input list and then to form groups by equality on these projected elements
+{-# INLINE groupWith #-}
+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 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', () #)