X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Data%2FIntSet.hs;h=36cac361a07f717f03a9aeba141b5494253c573b;hb=93b9a4ab1adffb656b3f65ac5a9ebe89d10adef8;hp=720b93782243bbf69b3e9ca21013e9a1c4b1af4c;hpb=2701ac4127cbc37e6d1069e2f5240a1e0ec1e479;p=ghc-base.git

diff --git a/Data/IntSet.hs b/Data/IntSet.hs
index 720b937..36cac36 100644
--- 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