[project @ 2005-03-15 13:38:27 by simonmar]

[ghc-base.git] / Data / Set.hs

diff --git a/Data/Set.hs b/Data/Set.hs
index fb58ce2..f321abf 100644 (file)
--- a/Data/Set.hs
+++ b/Data/Set.hs
@@ -112,7 +112,6 @@ module Data.Set  (
             ) where
 
 import Prelude hiding (filter,foldr,null,map)
-import Data.Monoid
 import qualified Data.List as List
 import Data.Typeable
 
@@ -250,7 +249,7 @@ isSubsetOfX t Tip = False
 isSubsetOfX (Bin _ x l r) t
   = found && isSubsetOfX l lt && isSubsetOfX r gt
   where
-    (found,lt,gt) = splitMember x t
+    (lt,found,gt) = splitMember x t
 
 
 {--------------------------------------------------------------------
@@ -347,7 +346,7 @@ intersect' t (Bin _ x l r)
   | found     = join x tl tr
   | otherwise = merge tl tr
   where
-    (found,lt,gt) = splitMember x t
+    (lt,found,gt) = splitMember x t
     tl            = intersect' lt l
     tr            = intersect' gt r
 
@@ -427,7 +426,7 @@ elems s
 {--------------------------------------------------------------------
   Lists 
 --------------------------------------------------------------------}
--- | /O(n)/. Convert the set to an ascending list of elements.
+-- | /O(n)/. Convert the set to a list of elements.
 toList :: Set a -> [a]
 toList s
   = toAscList s
@@ -506,15 +505,6 @@ instance Ord a => Ord (Set a) where
     compare s1 s2 = compare (toAscList s1) (toAscList s2) 
 
 {--------------------------------------------------------------------
-  Monoid 
---------------------------------------------------------------------}
-
-instance Ord a => Monoid (Set a) where
-    mempty = empty
-    mappend = union
-    mconcat = unions
-
-{--------------------------------------------------------------------
   Show
 --------------------------------------------------------------------}
 instance Show a => Show (Set a) where
@@ -616,13 +606,13 @@ split x (Bin sy y l r)
 
 -- | /O(log n)/. Performs a 'split' but also returns whether the pivot
 -- element was found in the original set.
-splitMember :: Ord a => a -> Set a -> (Bool,Set a,Set a)
-splitMember x Tip = (False,Tip,Tip)
+splitMember :: Ord a => a -> Set a -> (Set a,Bool,Set a)
+splitMember x Tip = (Tip,False,Tip)
 splitMember x (Bin sy y l r)
   = case compare x y of
-      LT -> let (found,lt,gt) = splitMember x l in (found,lt,join y gt r)
-      GT -> let (found,lt,gt) = splitMember x r in (found,join y l lt,gt)
-      EQ -> (True,l,r)
+      LT -> let (lt,found,gt) = splitMember x l in (lt,found,join y gt r)
+      GT -> let (lt,found,gt) = splitMember x r in (join y l lt,found,gt)
+      EQ -> (l,True,r)
 
 {--------------------------------------------------------------------
   Utility functions that maintain the balance properties of the tree.