complSeq = T.map complNt . toDna
  where
    complNt nt = case nt of
      'A' -> 'T'
      'T' -> 'A'
      'G' -> 'C'
      'C' -> 'G'
      _   -> 'N'
complSeq = T.map complNt . toDna
  where
    complNt nt = case nt of
      'A' -> 'T'
      'T' -> 'A'
      'G' -> 'C'
      'C' -> 'G'
      _   -> 'N'
complSeq = T.map complNt . toDna
  where
    complNt nt = case nt of
      'A' -> 'T'
      'T' -> 'A'
      'G' -> 'C'
      'C' -> 'G'
      _   -> 'N'