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-constraints-plugin.htm... http://qbaylogic.com/blog/2016/08/17/solving-knownnat-custom-operations.html Regards, Christiaan