[Haskell-beginners] A first try
apfelmus at quantentunnel.de
Sun Jun 26 14:25:38 CEST 2011
David Place wrote:
> Heinrich Apfelmus wrote:
>> Personally, I think that lazy IO is not a weakness and works
>> extremely well for prototyping. In contrast, I find IterateeIO to
>> be ugly and non-idiomatic Haskell, since it exposes implementation
>> details and is not built on an algebraic "combinators & laws"
>> approach. Being challenging to understand is not a substitute for
> Interesting, I appreciate your point of view. My experience with
> Lazy IO is that its non-determinism breaks down the
> algebraic/equational intuition. In order to manage handle resources,
> I must have in mind too many operational details.
Well, one could say that it's the fault of the operating system for not
doing garbage collection on file handles (c.f. Oberon).
> I feel that iteratee IO encapsulates these in nice compositional
What about the combinator
withFile :: FilePath -> (String -> a) -> IO a
withFile name f = bracket (openFile name ReadMode) hClose $ \h ->
evaluate . f =<< hGetContents h
? It gives you the same thing as Iteratees - a way to apply a function
to the contents of a file - without the need to rewrite all the existing
list functions like map , lines , words , and so on.
> I agree that it's not very beautiful, though. My feeling is that it
> is not quite finished. Perhaps there are a couple of more insights
> that will make it really nice.
I'm all for beauty in programming.
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