[Haskell-cafe] In " returnIO x = IO $ \ s -> (# s, x #)" what are the # symbols?

[Michael Snoyman]

You may also like this Wiki page about state tokens[1] (note: I'm the
author).

[1] https://wiki.haskell.org/Evaluation_order_and_state_tokens

On Mon, Jul 13, 2015 at 5:25 PM Tikhon Jelvis <tikhon at jelv.is> wrote:

> That's special syntax to make an unboxed tuple. See the manual section on
> unboxed types[1].
>
> [1]:
> https://downloads.haskell.org/~ghc/7.6.3/docs/html/users_guide/primitives.html
>
> On Mon, Jul 13, 2015 at 5:23 PM, Jeffrey Brown <jeffbrown.the at gmail.com>
> wrote:
>
>> That appears here:
>> http://hackage.haskell.org/package/base-4.8.0.0/docs/src/GHC-Base.html#line-1057
>>
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