isSubsetOfX (Bin _ x l r) t
  = found && isSubsetOfX l lt && isSubsetOfX r gt
  where
    (lt,found,gt) = splitMember x t
#if __GLASGOW_HASKELL__ >= 700

isSubsetOfX (Bin _ x l r) t
  = found && isSubsetOfX l lt && isSubsetOfX r gt
  where
    (lt,found,gt) = splitMember x t
#if __GLASGOW_HASKELL__ >= 700

isSubsetOfX (Bin _ x l r) t
  = found && isSubsetOfX l lt && isSubsetOfX r gt
  where
    (lt,found,gt) = splitMember x t
#if __GLASGOW_HASKELL__ >= 700
