Question

I am a beginner, and write implementation of hangman in haskell.
Necessary to show guessed characters in ‘*‘-like string, currently I use that code:

proceed char word progress = let zprog = zip progress [0..] in
    foldl (\a x -> a ++ [fst x]) "" $ map (f char word) zprog where    
        f c w el = 
            if c == w !! (snd el) then
                (c, snd el)
            else
                el

If word was “shadow” and progress like “******”, char = ‘s’ function return “s****”.

How can I rewrite that function? I see that its not clean solution.
Solution (by @luqui):

proceed char = zipWith combine where
    combine x y
        | x == char = char
        | otherwise = y

(“word” and “progress” arguments transfers to zipWith becose haskell’s eta-reduction)

Answer 1

You are right to think of zip, you just seem to have done some extra work. See if you can write a suitable helper function combine:

proceed char word progress = zipWith combine word progress
    where
    combine :: Char -> Char -> Char
    combine = ?