[Haskell-beginners] what does (# a, s #) mean?

[Henk-Jan van Tuyl]

On Sun, 10 Apr 2011 19:29:38 +0200, Amitava Shee <amitava.shee at gmail.com>  
wrote:

> I came across this definition in ghc source
>
> $GHC/compiler/utils/State.hs
> =======================
> newtype State s a = State { runState' :: s -> (# a, s #) }
>
>
> What does the construct (# a, s #) mean?
>

This is an unboxed tuple, see:
   http://www.haskell.org/ghc/docs/latest/html/users_guide/primitives.html#unboxed-tuples

Regards,
Henk-Jan van Tuyl


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