Re: [Haskell-beginners] Improve my FFI code please...

On Friday 21 January 2011 16:43:10, sean@objitsu.com wrote:

Quoting Christian Maeder :

...

Am 21.01.2011 00:35, schrieb Sean Charles:

...

wiiClose :: Ptr Word8 -> IO Bool wiiClose wptr = do response <- c_wiimote_close wptr case response of 0 -> return True _ -> return False

This can be rewritten to:

wiiClose = fmap (== 0) . c_wiimote_close

...

case status of True -> putStrLn "OK" False -> putStrLn "FAIL"

Matching Bool values use "case" is no good style:

putStrLn (if status then "OK" else "FAIL")

Christian

That's clever but you'd have to *know* haskell to *know* you could do that! Point-free (pointless!) is something I have yet to fully tackle, it looks like a great thing. Function composition is something else for my brain to remember exists in the language!

IIUC: given a Ptr8 Word, call c_wiimote close then 'functor map' the 'section' (== 0) over the single entry in the list... what list? I am confused again because I cannot see a list, c_wiimote_close answers a pointer.

No list here, fmap 'lifts' a function to any Functor. Here the Functor is IO. Generally, for any Monad which is also an instance of Functor (any Monad should be), fmap function monadicThingy ought to be the same as do value <- monadicThingy return (function value) which is the sugared version of monadicThingy >>= return . function

I understand (== 0) rather than (0 ==) though, that's something!

Both should be the same function.

Thanks for your time.

:)