Re: [Haskell-cafe] Why does this work: 'instance Num (Show a) where'

No, this is in an otherwise empty file. On Tue, Nov 04, 2014 at 08:46:08PM +1100, Ivan Lazar Miljenovic wrote:

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