[Haskell] Files and lazyness
tomasz.zielonka at gmail.com
Mon Aug 1 16:38:53 EDT 2005
On Thu, Jul 28, 2005 at 08:01:17PM +0200, Diego y tal wrote:
> I understand that this is caused by the lazyness,
No, it is caused by mixing laziness with side-effects, which happens
when you use getContents/readFile.
> that doesn't evaluate the expression "x <- readFile fEntrada" until
> it's necessary,
"x <- readFile fEntrada" is not an expression.
> but.. is it normal that we have to think about this "problem" when
You just have to know, which functions mix laziness and side-effects
by using unsafeInterleaveIO (readFile, getContents, hGetContents).
> I find this a great disadvantage as oppose of the imperative paradigm,
I wouldn't say this is a great disadvantage of Haskell, because:
a) the imperative paradigm is available in Haskell
b) readFile is a bit of hack, because it uses laziness where the order
of execution matters (it uses unsafeInterleaveIO). It is generally
known that readFile should be used only for the simplest I/O tasks.
c) there are other ways to complete the task (however, some of them
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