For this function,showGame, and the expected output, anyone can give me a hand to make this work ?
import System.IO
type Symbol = Int
showGame :: [Symbol] => IO ()
showGame xs =
let x = mapM_ (replicate '*') xs
putStrLn x
The output should be:
1: *
2: **
3: ***
with
[Symbol] = [1,2,3]
After fixing a few mistakes in your code we get this:
type Symbol = Int
showGame :: [Symbol] -> IO ()
showGame xs =
mapM_ (\x -> putStrLn $ show x ++ ": " ++ replicate x '*') xs
main = showGame [1..3]
Output:
1: *
2: **
3: ***
forM (mapM with the arguments flipped) because then it reads like a foreach loop.It looks like you want:
let x = fmap (flip replicate $ '*') [1,2,3]
mapM_ putStrLn x
mapM_ applies a monadic action over a list but discards the results. This is what you want to print, since there is no useful result. However you do want the a result when creating the lists to display. Here you can just use fmap (or map since the input is a list) to create a list for each input list element.
(`replicate` '*') is significantly more readable than the equivalent with flip, and in fact easier to understand (though it actually uses more advanced features of the language).
showin Haskell typically provide aStringrather than an IO action. You might want to name thisprintGameinstead.