Re: [Haskell-cafe] object oriented technique

On Wed, Mar 30, 2011 at 6:52 AM, Tad Doxsee wrote:

Greg,

Thanks for your help.  Is there any significant difference between using existential quantification

data ShapeD = forall s. ShapeC => ShapeD s

versus a GADT

data ShapeD  where  ShapeD :: ShapeC s => s -> ShapeD

I'm not sure I understood what you meant by "You don't need to write more typeclass instances this way."

Sorry, I misspoke -- they're equivalent. Personally I find the existential easier to read. G -- Gregory Collins