Re: [Haskell-cafe] Rotating backdrop (aka learning Haskell)

Quoth Derek Elkins on Tue, May 20, 2008 at 11:45:57 -0500

On Tue, 2008-05-20 at 10:55 +0200, Ketil Malde wrote:

...

Yann Golanski writes:

...

1- Get a list out of a file: I managed to do that using the following:

parseImageFile :: FilePath -> IO [String] parseImageFile file = do inpStr <- readFile file return $ filter (/="") (breaks (=='\n') inpStr)

Nice, simple and I understand what it is doing.

Can be improved:

breaks (=='\n') == lines -- easier to read, no? filter (/="") == filter (not . null) -- more polymorphic, not important here do x <- expr1 == expr1 >>= return . expr2 return $ expr2 x -- i.e. "readFile f >>= return . filter (not.null) . lines"

do x <- expr1; return $ expr2 x == expr1 >>= return . expr2 == liftM expr2 expr1 -- or fmap (a.k.a. <$>) if you like

So, liftM (filter (not . null) . lines) readFile alternatively, filter (not . null) . lines <$> readFile

I'm sorry, this is a little beyond me. Could you elaborate a little more on what this actually does? -- yann@kierun.org -= H+ =- www.kierun.org PGP: 009D 7287 C4A7 FD4F 1680 06E4 F751 7006 9DE2 6318