[Haskell-cafe] avoid to print empty string

[MarLinn]

> i have this in a Monad IO:
>
>  forM_ fltrdNamesBDs $ \(name,bdSidonie,bdWDS) ->
>           if (bdWDS /= bdSidonie)
>           then
>              putStrLn $  name ++ " " ++ (show (bdSidonie :: Maybe Float))
> ++ " " ++ show (bdWDS :: Maybe Float) ++ " " ++ show (bdWDS == bdSidonie)
>           else
>              putStr ""
>
> is there a way to remove the silly putStr "" that output an empty string, i
> tried with when.... but as when return Nothing in case of False it fails to
> compile


I don't see the problem with when? This (in the expanded version)
doesn't work?

	forM_ fltrdNamesBDs $ \(name,bdSidonie,bdWDS) -> when (bdWDS /= bdSidonie) $ showStuff name bdSidonie bdWDS

As an extra remark, whenever I want to output a whole bunch of stuff in
a row like this, I like to refactor into a concat, just to make the code
more readable. If I can factor out the types, all the better:

	where
	    showStuff :: String -> Maybe Float -> Maybe Float -> IO ()
	    showStuff name bdSidonie bdWDS = putStrLn $ concat [name," ",show bdSidonie," ",show bdWDS," False"]

Or even

	    showStuff :: String -> Maybe Float -> Maybe Float -> IO ()
	    showStuff name bdSidonie bdWDS = putStrLn $ Data.List.intercalate " " [name,show bdSidonie,show bdWDS,show False]


Cheers.

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