waveChunk :: String -> Maybe WAVE_CHUNK
waveChunk str
  | str == "fmt " = Just WAVE_FMT
  | str == "data" = Just WAVE_DATA
  | P.length str == 4 = Just $ WAVE_OTHER str
  | otherwise = Nothing
waveChunk :: String -> Maybe WAVE_CHUNK
waveChunk str
  | str == "fmt " = Just WAVE_FMT
  | str == "data" = Just WAVE_DATA
  | P.length str == 4 = Just $ WAVE_OTHER str
  | otherwise = Nothing
waveChunk str
  | str == "fmt " = Just WAVE_FMT
  | str == "data" = Just WAVE_DATA
  | P.length str == 4 = Just $ WAVE_OTHER str
  | otherwise = Nothing