Guarantees for ST and IO shared in common?

[Christopher Allen]

Perfect, thank you very much Simon! I know you're busy so you taking the
time to answer questions like this is a much appreciated gift.

On Thu, Feb 4, 2016 at 6:11 AM, Simon Peyton Jones <simonpj at microsoft.com>
wrote:

> that the mechanism for preventing things like reordering operations or
> spurious sharing is shared in common between ST and IO via State#
>
>
>
> Yes. It’s pure data dependency, no more and no less. Operations in both ST
> and IO take a State# token as input, and produce one as output.  So of
> course to get the input one, all preceding operations must be done first.
> Simple!
>
>
>
> Simon
>
>
>
> *From:* ghc-devs [mailto:ghc-devs-bounces at haskell.org] *On Behalf Of *Christopher
> Allen
> *Sent:* 03 February 2016 23:30
> *To:* ghc-devs at haskell.org
> *Subject:* Guarantees for ST and IO shared in common?
>
>
>
> Underlying ST is: GHC.Prim.State# s -> (# GHC.Prim.State# s, a #)
>
>
>
> Underlying IO is: GHC.Prim.State# GHC.Prim.RealWorld
>
>         -> (# GHC.Prim.State# GHC.Prim.RealWorld, a #)
>
>
>
> Based on the (very helpful!) conversation I had on the #ghc IRC channel,
> it seems to me that the mechanism for preventing things like reordering
> operations or spurious sharing is shared in common between ST and IO via
> State#. Is this accurate? I believe the exception is how RealWorld is used
> w/ IO but we can put that off for this question.
>
>
>
> If anyone could confirm this understanding that would be helpful. If
> anyone could point out exceptions to this notion, I'd very much appreciate
> that as well.
>
>
>
>
>
> Thanks again for everyone's time.
>
>
>
> --
>
> Chris Allen
>
> Currently working on http://haskellbook.com
> <https://na01.safelinks.protection.outlook.com/?url=http%3a%2f%2fhaskellbook.com&data=01%7c01%7csimonpj%40064d.mgd.microsoft.com%7c437e21b733ab4fa4895908d32cf1fd68%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=PPVWa%2bCUw8gEWIOVEyJNcOKuGGmZBtfvXg0wsA2jS2Y%3d>
>



-- 
Chris Allen
Currently working on http://haskellbook.com
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