[Haskell-cafe] minor refactoring problem

[Martin DeMello]

On Tue, Nov 29, 2011 at 12:35 AM, Stefan Holdermans
<stefan at vectorfabrics.com> wrote:

> Have you considered abstracting over the bits in which importFile and loadFile differ? For example:
>
>  processFile :: (String -> IO [PairBox]) -> Editor -> String -> IO ()
>  processFile f ed path = do
>    s <- readFile path
>    ps <- f s
>    es <- return $ V.fromList ps
>    writeIORef ed es
>
>  importFile = processFile (mapM (\x -> makePair (x, "")) . lines)
>  loadFile   = processFile (mapM makePair . parseFile)

This was what I had tried; my issue was that the resulting code looked
harder rather than easier to read, so it felt more like golfing than
refactoring.

> Or, alternatively:
>
>  processFile :: (String -> [a]) -> (a -> IO PairBox) -> Editor -> String -> IO ()
>  processFile f g ed path = do
>    s <- readFile path
>    ps -> mapM g (f s)
>    es -> return $ V.fromList ps
>    writeIORef ed es
>
>  importFile = processFile lines (\x -> makePair (x, ""))
>  loadFile   = processFile parseFile makePair

This does look significantly nicer - I hadn't thought of splitting it
into two functions rather than one, but it makes the code look much
less cluttered. (The trick with `flip` is tempting, but again at the
cost of having to peer rather too closely at the implementation of
processFile when reading the code). Thanks!

martin