[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


---

This e-mail may contain confidential and/or privileged information. If you 
are not the intended recipient (or have received this e-mail in error) 
please notify the sender immediately and destroy this e-mail. Any 
unauthorized copying, disclosure or distribution of the material in this 
e-mail is strictly forbidden.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20071031/78e21347/attachment.htm