diff --git a/indexation.cabal b/indexation.cabal
--- a/indexation.cabal
+++ b/indexation.cabal
@@ -1,5 +1,5 @@
 name: indexation
-version: 0.6.4.1
+version: 0.8
 category: Data
 synopsis: Tools for entity indexation
 description: A set of tools for indexing entities
@@ -43,7 +43,7 @@
     contravariant >=1.4 && <2,
     deepseq >=1.4.3 && <2,
     deferred-folds >=0.9.6 && <0.10,
-    dense-int-set >=0.2 && <0.3,
+    dense-int-set >=0.3 && <0.4,
     focus >=1.0.1 && <1.1,
     foldl >=1 && <2,
     hashable >=1 && <2,
diff --git a/library/Indexation/Functions.hs b/library/Indexation/Functions.hs
--- a/library/Indexation/Functions.hs
+++ b/library/Indexation/Functions.hs
@@ -34,9 +34,15 @@
 lookupNewIndex :: Index entity -> ReindexTable entity -> Maybe (Index entity)
 lookupNewIndex (Index oldIndexInt) (ReindexTable mapVector) = fmap Index (join (mapVector Vector.!? oldIndexInt))
 
-mergeIndexSets :: IndexSet entity -> IndexSet entity -> IndexSet entity
-mergeIndexSets (IndexSet a) (IndexSet b) = IndexSet (DenseIntSet.intersection (DenseIntSet.compose a <> DenseIntSet.compose b))
+intersectIndexSets :: [IndexSet entity] -> IndexSet entity
+intersectIndexSets = IndexSet . DenseIntSet.intersections . coerce
 
+uniteIndexSets :: [IndexSet entity] -> IndexSet entity
+uniteIndexSets = IndexSet . DenseIntSet.unions . coerce
+
+invertIndexSet :: IndexSet entity -> IndexSet entity
+invertIndexSet (IndexSet x) = IndexSet (DenseIntSet.invert x)
+
 topCountedIndexSet :: Int -> IndexCounts a -> IndexSet a
 topCountedIndexSet amount (IndexCounts countVec) = IndexSet (DenseIntSet.topValueIndices compare amount countVec)
 
@@ -44,7 +50,7 @@
 indexSetByMinCount min (IndexCounts countVec) = IndexSet (DenseIntSet.filteredIndices (>= min) countVec)
 
 countIndexSet :: IndexSet a -> Int
-countIndexSet (IndexSet set) = DenseIntSet.size set
+countIndexSet (IndexSet set) = DenseIntSet.population set
 
 newIndexToOldIndexTable :: IndexSet a -> EntityTable (Index a)
 newIndexToOldIndexTable (IndexSet set) = EntityTable (DenseIntSet.presentElementsVector set Index)