[Haskell-cafe] monad constraint + record update
byorgey at seas.upenn.edu
Tue Dec 23 14:28:29 EST 2008
On Mon, Dec 22, 2008 at 06:19:07PM +0100, Peter Padawitz wrote:
> I'd like to define a monad Set for types in the class Eq. But how can the
> arguments of Set be constrained when Set is defined as an instance of
> Monad? instance Eq a => Monad Set where ... obviously cannot work.
> Is there a standard update function for fields in data types, something
> that OO programmers do with assignments like obj.attr := value ?
Note there is already a package on Hackage to do exactly this, rmonad.
More information about the Haskell-Cafe