f.hs

sepBy1 :: Parser a -> Parser b -> Parser [a]
sepBy1 p s = liftA2 (:) p (FP.many (s >> p))

crate :: Parser MCrate
crate = do
  b <- FP.lookahead FP.anyWord8
  case BS.w2c b of
    ' '  -> Nothing <$ $(FP.string "   ")
    '['  -> FP.skip 1 >> (Just <$> FP.anyCharASCII) <* $(FP.char ']')
    '\n' -> FP.empty
    _    -> FP.err "bad input"

eol :: Parser ()
eol = $(FP.char '\n')

hstack :: Parser [MCrate]
hstack = sepBy1 crate $(FP.char ' ') <* eol