diff --git a/happstack-ixset.cabal b/happstack-ixset.cabal
--- a/happstack-ixset.cabal
+++ b/happstack-ixset.cabal
@@ -1,5 +1,5 @@
 Name:                happstack-ixset
-Version:             0.2.1
+Version:             0.3.1
 Synopsis:            Efficient relational queries on Haskell sets. 
 Description:         Just pick which parts of your data structures you want indexed using an easy to use template-haskell function. Spare yourself the need to write, run, and maintain code that marshalls your data to/from an external relational database just for efficient queries. happstack-ixset relies on generics and TH to spare you the boilerplate normally required for such tasks. 
 License:             BSD3
@@ -9,8 +9,13 @@
 homepage:            http://happstack.com
 Category:            Web, Distributed Computing
 Build-Type:          Simple
-Cabal-Version:       >= 1.2.3
+Cabal-Version:       >= 1.6
 
+source-repository head
+    type:     darcs
+    subdir:   happstack-ixset
+    location: http://patch-tag.com/publicrepos/happstack
+
 flag base4
 
 Flag tests
@@ -24,8 +29,8 @@
     Build-Depends:     base < 4
 
   Build-Depends:       containers,
-                       happstack-data >= 0.2.1 && < 0.3,
-                       happstack-util >= 0.2.1 && < 0.3,
+                       happstack-data >= 0.3.1 && < 0.4,
+                       happstack-util >= 0.3.1 && < 0.4,
                        mtl,
                        syb-with-class,
                        template-haskell
diff --git a/src/Happstack/Data/IxSet.hs b/src/Happstack/Data/IxSet.hs
--- a/src/Happstack/Data/IxSet.hs
+++ b/src/Happstack/Data/IxSet.hs
@@ -163,6 +163,12 @@
 noCalcs :: t -> ()
 noCalcs _ = ()
 
+{- | Helper function for automatically building an Indexable instance
+   from a data type, e.g. @data Foo = Foo Int String@ and
+   @$(inferIxSet "FooDB" ''Foo 'noCalcs [''Int,''String])@ will 
+   build a type synonym @type FooDB = IxSet Foo@ with @Int@ and
+   @String@ as indexes.
+-} 
 inferIxSet :: String -> TH.Name -> TH.Name -> [TH.Name] -> Q [Dec]
 inferIxSet ixset typeName calName entryPoints
     = do calInfo <- reify calName
@@ -287,6 +293,13 @@
 getOneOr :: Ord a => a -> IxSet a -> a
 getOneOr def = fromMaybe def . getOne
 
+-- | return True if the IxSet is empty, False otherwise.
+null :: IxSet a -> Bool
+null (IxSet (Ix ix:_)) = Map.null ix
+null (ISet lst)        = List.null lst
+null (IxSet [])        = True
+null _ = error "IxSet.null: unexpected match"
+
 -- set operations
 
 -- | An infix intersection operation
@@ -469,4 +482,3 @@
 instance (Show a,Indexable a b,Data a,Ord a) => Monoid (IxSet a) where
     mempty=empty
     mappend = union
-