[Haskell-cafe] FGL instance constraint

[Sebastian Fischer]

On May 1, 2010, at 8:08 AM, Ivan Lazar Miljenovic wrote:

>> * I can't redefine the Graph methods to introduce the (Cls a)
>> constraint [reasonable]
>
> Not sure if you can.

I think Kevin means that he cannot change the signature of the methods  
in the Graph class because those are defined in the FGL package.

> You're putting the constraint in the wrong places: put the "(Cls a)  
> => "
> in the actual functions where you need it.

Those seem to be the methods of the Graph class, where he can't place  
the constraints. Kevin may have a version of  makeGraph  with  
additional constraints but cannot use it to to define a  Graph   
instance.

Sebastian

-- 
Underestimating the novelty of the future is a time-honored tradition.
(D.G.)