Re: [Haskell-cafe] If the local variable can be changed ...

Yes, we can imitate all of it (such as `when`, `until` and `for`) because haskell is a good DSL language. However, i feel it will be more convenient if the language itself supports all these fundations. jmillikin wrote:

If your code performs a common task (such as conversion, accumulation, testing), then you should use higher-level constructs than a for loop. Using map, filter, foldr, and foldl will make it easier to write correct code.

If you'd like to imitate a for loop exactly -- that is, to perform some action multiple times -- it's very easy to create a pure function. We do not have to stoop to mutable variables.

------------------------------------------------- for :: Monad m => a -> (a -> Bool) -> (a -> a) -> (a -> m ()) -> m () for start test step body = loop start where loop x = if test x then body x >> loop (step x) else return ()

main = for 0 (< 100) (+ 1) $ \i -> do -- do something with i print i -------------------------------------------------

On Tue, Mar 9, 2010 at 16:25, zaxis wrote:

...

In FP the variable can not be changed once created. Yes, it has much advantage . However, i feel it is too strict.   As we know, the local variable is allocated on stack which is thread safe.

So if the local variable can be changed, then we can use loop, etc. same as imperative languages. For example, for (i=0; i<100; i++)  where `i` is a local variable in function.

Any suggestion is appreciated!

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