[Haskell-cafe] [ANN] ghc-typelits-knownnat-0.2: Solving GHCs KnownNat constraints

[Edward Kmett]

I have to admit that is a heck of a lot easier to use than what I have:

https://github.com/ekmett/constraints/blob/master/src/Data/Constraint/Nat.hs

=)

-Edward

On Wed, Aug 17, 2016 at 9:11 AM, Christiaan Baaij <
christiaan.baaij at gmail.com> wrote:

> Hi,
>
> If you have ever worked with `GHC.TypeLits`, then you have probably
> encountered an error very similar to:
>
> >    • Could not deduce (KnownNat (n + 2))
> >        arising from a use of ‘natVal’
> >      from the context: KnownNat n
>
> i.e. where GHC cannot infer a `KnownNat (n+2)` constraint, even though a
> `KnownNat n` constraint is already given.
>
> Enter http://hackage.haskell.org/package/ghc-typelits-knownnat
> A type-checker plugin that can automatically derive "complex" KnownNat
> constraints from simpler ones.
>
> To use it, you simply add the
>
> {-# OPTIONS_GHC -fplugin GHC.TypeLits.KnownNat.Solver #-}
>
> pragma to the top of your file.
>
> If you want to know more, you can also check out the corresponding blog
> posts:
>
> http://qbaylogic.com/blog/2016/08/10/solving-knownnat-constr
> aints-plugin.html
> http://qbaylogic.com/blog/2016/08/17/solving-knownnat-custom
> -operations.html
>
> Regards,
>
> Christiaan
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/haskell-cafe/attachments/20160817/2cc83bb2/attachment.html>