Re: [Haskell-beginners] Heterogeneous Lists

Hi. On 28 May 2013 18:07, Frerich Raabe wrote:

On May 28, 2013, at 12:36 AM, harry wrote:

...

Every OO language which supports generics allows a declaration such as List<Show> alist, where Show is an interface. Any type implementing Show can be put in alist, and any Show operation can be performed on the alist's members. No casts, wrappers, or other special types and plumbing are needed.

Why isn't it possible to do this directly in Haskell?

My impression is that you often don't have this requirement, since functions are first-class values and you can treat them as closures.

This might also be relevant: http://okmij.org/ftp/Computation/Existentials.html Hope this helps, Ozgur.