[Haskell-beginners] mapM etc.

[Sean Perry]

On Jul 1, 2011, at 1:08 PM, Dennis Raddle wrote:

> It's been about a year since I used Haskell and I'm rusty. I think I knew how to do this once, but I need a reminder.
> 
> I've got some functions:
> 
> getDeviceInfo :: Int -> IO DeviceInfo
> 
> name :: DeviceInfo -> String
> 
> I want to do something like
> 
> func :: IO ()
> func = do 
>   ds <- mapM getDeviceInfo [0..10]
>   mapM_ (print . name) ds
> 
> Is there a way to combine 'getDeviceInfo', 'name', and 'print' in one line?
> 

I end up with either:

join . fmap (mapM_ (print . name)) $ mapM getDeviceInfo [1..10]

or

mapM getDeviceInfo [1..10] >>= mapM_ (print . name)

You can move the call to name into the mapM using (fmap name . getDeviceInfo) but I left them separate to match your code better.