Hello Gene, Monday, August 21, 2006, 12:42:17 PM, you wrote:
being able to use +,* on any of the numeric types... but can you have a list of type [Num] ?? I thought that it had to be the base types of Int, Integer, Float, Double etc.. No?
you can, using existentials: data Number = forall a. (Num a, Show a) => Num a main = print [Num (1::Int), Num (1.1::Double), Num (1::Integer)] but that is not really very important. in my own practice, homogeneous lists are suffice in almost all cases you can read recent discussion on this in this topic, or look at http://haskell.org/haskellwiki/OOP_vs_type_classes, where John Meacham and me describes how existentials can partially emulate OOP classes -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com