You can make it polykinded: {-# LANGAUGE PolyKinds #-} class HasIniConfig (a :: k) where   getConfig ... And then you can use both types of kind ProjectionType, and also "regular types" of kind Type. On 6/13/24 18:32, PICCA Frederic-Emmanuel wrote:

Hello,

I have a class

class HasIniConfig where getConfig ...

a kind using DataKind

data ProjectionType = TypeA | TypeB ...

I would like to create instance for each 'TypeX

But when I try to write an instance

I get this error

src/Hkl/Binoculars/Projections/QCustom.hs:195:23: error: • Expected a type, but ‘'QCustomProjection’ has kind ‘ProjectionType’ • In the first argument of ‘HasIniConfig’, namely ‘'QCustomProjection’ In the instance declaration for ‘HasIniConfig 'QCustomProjection’ | 195 | instance HasIniConfig 'QCustomProjection where | ^^^^^^^^^^^^^^^^^^

I should add class HasIniConfig (a :: ProjectionType) where

But in that cas I can not create instance for other type, and I need to :)

I would be glade if someone could explain how to all this.

Thanks

Frederic _______________________________________________ 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.