[project @ 2005-04-21 09:40:41 by simonmar]

[haskell-directory.git] / Data / Set.hs

diff --git a/Data/Set.hs b/Data/Set.hs
index 7e07fbe..eb41f94 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
 
@@ -208,6 +207,8 @@ singleton x
   Insertion, Deletion
 --------------------------------------------------------------------}
 -- | /O(log n)/. Insert an element in a set.
+-- If the set already contains an element equal to the given value,
+-- it is replaced with the new value.
 insert :: Ord a => a -> Set a -> Set a
 insert x t
   = case t of
@@ -290,7 +291,9 @@ unions ts
   = foldlStrict union empty ts
 
 
--- | /O(n+m)/. The union of two sets. Uses the efficient /hedge-union/ algorithm.
+-- | /O(n+m)/. The union of two sets, preferring the first set when
+-- equal elements are encountered.
+-- The implementation uses the efficient /hedge-union/ algorithm.
 -- Hedge-union is more efficient on (bigset `union` smallset).
 union :: Ord a => Set a -> Set a -> Set a
 union Tip t2  = t2
@@ -427,7 +430,7 @@ 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 +509,6 @@ 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