hw.patch

index 3a6d622..628027e 100644
--- a/src/HaskellWorks/Data/RankSelect/Internal/BitSeq.hs
+++ b/src/HaskellWorks/Data/RankSelect/Internal/BitSeq.hs
@@ -85,8 +85,8 @@ instance HW.Cons BitSeq where
 instance HW.Snoc BitSeq where
   snoc (BitSeq ft) b = BitSeq $ case FT.viewr ft of
     lt :> Elem w nw -> if nw >= 0 && nw < 64
-      then Elem (w .|. (bw .<. nw)) (nw + 1) <| lt
-      else Elem bw 1                         <| lt
+      then lt |> Elem (w .|. (bw .<. nw)) (nw + 1)
+      else ft |> Elem bw 1
     FT.EmptyR        -> FT.singleton (Elem bw 1)
     where bw = if b then 1 else 0

@@ -99,6 +99,9 @@ instance Semigroup BitSeq where
       FT.EmptyL -> tr
     FT.EmptyR -> FT.empty

+instance Monoid BitSeq where
+  mempty = BitSeq mempty
+
 instance Select1 BitSeq where
   select1 (BitSeq ft) n = case FT.split (atPopCountBelow n) ft of
     (lt, _) -> case FT.viewr lt of
@@ -112,7 +115,7 @@ instance Rank1 BitSeq where
   rank1 bs n = let (lt, _) = splitAt n bs in popCount1 lt

 instance PopCount1 BitSeq where
-  popCount1 (BitSeq ft) = measureBitCount (FT.measure ft :: Measure)
+  popCount1 (BitSeq ft) = measurePopCount (FT.measure ft :: Measure)

 (|>#) :: BitSeqFt -> Elem -> BitSeqFt
 (|>#) ft e@(Elem _ wn) = if wn > 0 then ft |> e else ft