Re: [Haskell-cafe] Polymorphic (typeclass) values in a list?

On Oct 19, 2007, at 12:11 , Sebastian Sylvan wrote:

On 19/10/2007, Kalman Noel wrote:

...

data ExistsNumber = forall a. Num a => Number a

I'm without a Haskell compiler, but shouldn't that be "exists a."?

The problem is that "exists" is not valid in either Haskell 98 or any current extension, whereas "forall" is a very common extension. But you can simulate "exists" via "forall", which is the thrust of these approaches. -- brandon s. allbery [solaris,freebsd,perl,pugs,haskell] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH