[Haskell-cafe] Declaring variance of class parameters?

Ross Paterson ross at soi.city.ac.uk
Tue Feb 27 14:03:42 EST 2007

On Tue, Feb 27, 2007 at 02:00:29PM -0500, Jacques Carette wrote:
> If I have a class, say
> class Symantics repr where
>  int:: Int -> repr Int
> and so on, I would like to *require* that 'repr' be covariant.  Is there 
> any way to do that?

	class Functor repr => Symantics repr

would be pretty close, and has the virtue of saying what you mean.

More information about the Haskell-Cafe mailing list