traceSubseq :: Show a => String -> SubseqExtractor' n a -> SubseqExtractor' n a
traceSubseq s ex = SubseqExtractor' $ \n ->
  let rs = runSubseq ex n
  in  trace (if null s then show rs else s ++ ": " ++ show rs) rs
traceSubseq :: Show a => String -> SubseqExtractor' n a -> SubseqExtractor' n a
traceSubseq s ex = SubseqExtractor' $ \n ->
  let rs = runSubseq ex n
  in  trace (if null s then show rs else s ++ ": " ++ show rs) rs
traceSubseq s ex = SubseqExtractor' $ \n ->
  let rs = runSubseq ex n
  in  trace (if null s then show rs else s ++ ": " ++ show rs) rs