Is there a corresponding Show datatype? At least with 7.8.3, having just that line gives the following error: The first argument of ‘Num’ should have kind ‘*’, but ‘Show a’ has kind ‘Constraint’ In the instance declaration for ‘Num (Show a)’ On 4 November 2014 19:30, Tom Ellis wrote:

This is accepted by GHC 7.6.3. Is this a bug? What does it mean?

instance Num (Show a) where _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com http://IvanMiljenovic.wordpress.com

That's a bug. As you surmise, the code is meaningless. It seems to be fixed in 7.8. On Nov 4, 2014, at 3:30 AM, Tom Ellis wrote:

This is accepted by GHC 7.6.3. Is this a bug? What does it mean?

instance Num (Show a) where _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe