Re: [Haskell-cafe] Existencial Types

1 Dec 2009

      On Tue, Dec 1, 2009 at 11:21 AM, David Menendez  wrote:
...
On Tue, Dec 1, 2009 at 1:00 PM, rodrigo.bonifacio
 wrote:
...
Dear all, I wrote the following  types:
...
class Transformation t where
  (<+>) :: t -> SPLModel  -> InstanceModel -> InstanceModel
...
data Configuration = forall t . Transformation t => Configuration
(FeatureExpression, [t])
type ConfigurationKnowledge = [Configuration]
I would suggest doing away with the class in a case like this.

data Transformation = Transformation {
    (<+>) :: SPLModel -> InstanceModel -> InstanceModel
  }

data Configuration = Configuration FeatureExpression [Transformation]

I suspect that it was OO heritage that led you to want a class here?
Forget that!  :-)

Luke

Re: [Haskell-cafe] Existencial Types

Luke Palmer