remove conflicting import for nhc98

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

diff --git a/Data/IntSet.hs b/Data/IntSet.hs
index 720b937..36cac36 100644 (file)
--- a/Data/IntSet.hs
+++ b/Data/IntSet.hs
@@ -10,10 +10,11 @@
 --
 -- An efficient implementation of integer sets.
 --
--- This module is intended to be imported @qualified@, to avoid name
--- clashes with "Prelude" functions.  eg.
+-- Since many function names (but not the type name) clash with
+-- "Prelude" names, this module is usually imported @qualified@, e.g.
 --
--- >  import Data.IntSet as Set
+-- >  import Data.IntSet (IntSet)
+-- >  import qualified Data.IntSet as IntSet
 --
 -- The implementation is based on /big-endian patricia trees/.  This data
 -- structure performs especially well on binary operations like 'union'
@@ -46,6 +47,7 @@ module Data.IntSet  (
             , null
             , size
             , member
+            , notMember
             , isSubsetOf
             , isProperSubsetOf
             
@@ -209,6 +211,10 @@ member x t
       Tip y -> (x==y)
       Nil   -> False
     
+-- | /O(log n)/. Is the element not in the set?
+notMember :: Int -> IntSet -> Bool
+notMember k = not . member k
+
 -- 'lookup' is used by 'intersection' for left-biasing
 lookup :: Int -> IntSet -> Maybe Int
 lookup k t