Re: [Haskell-cafe] Strictness leak

[Jeff Polakow]

I forgot to send this reponse to haskell-cafe
earlier...

Hello,

> You mean for the IO monad, right?
> 
Sorry. I meant divergence is unavoidable for any strict
Monad, such as IO. 

However, sequence will always compute over the entire
list; if the resulting computation itself is lazy then the result can be
inspected lazily.

>    take 10 $ execWriter $ sequence $ repeat $ tell ([3]::[Int])
> 
This is a good example. Note that the computation of sequence itself is
infinite.

    snd $ runWriter $ sequence (repeat $
tell [3]) >>= return . take 10

will result in an infinite list, but

    fst $ runWriter $ sequence (repeat $
tell [3]) >>= return . take 10

will return a 10 element list.

-Jeff

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