Question

I am writing a Brainf*ck Interpreter in Haskell.

I am trying to print (chr (fromEnum $ getMem state)) which is just a conversion of a Word8 to Char.
Then I want to return a new state after the printing in a particular case which is

    '.' -> do hPutChar stdout (chr (fromEnum $ getMem state))
            hFlush stdout
            return state { prog_pointer = prog_pointer state}

I get this error message

The function `hPutChar' is applied to six arguments,
but its type `Handle -> Char -> IO ()' has only two

In a stmt of a 'do' block:
  hPutChar
    stdout
    (chr (fromEnum $ getMem state))
    hFlush
    stdout
    return
    (state {prog_pointer = prog_pointer state})

with this code

iterateBF :: BFState -> IO BFState
iterateBF state = case (program state !! prog_pointer state) of
    --some more cases here--
    '.' -> do hPutChar stdout (chr (fromEnum $ getMem state))
            hFlush stdout
            return state { prog_pointer = prog_pointer state}

I cant seem to figure out why I am getting this error.

After leftaroundabout and sabauma’s comments, i edited my code to be

iterateBF :: BFState -> IO BFState
iterateBF state = case (program state !! prog_pointer state) of
    --some more cases here--
    '.' -> do hPutChar stdout (chr (fromEnum $ getMem state))
           hFlush stdout
           return state { prog_pointer = prog_pointer state}

using only spaces this time.

However, I get parse error on input 'hFlush'

Anyone know why?

Answer 1

Building on leftaroundabout’s comment, you want

'.' -> do hPutChar stdout (chr (fromEnum $ getMem state))
          hFlush stdout
          return state { prog_pointer = prog_pointer state}

Note how all lines after the do are aligned with each other, not with the do.