[Haskell-cafe] Data declaration vs type classes

[Tom Ellis]

On Fri, Jan 08, 2016 at 05:55:45PM +0800, Lian Hung Hon wrote:
> How should one go about deciding to use data or class?  Is there a
> semantic difference?

Classes are not first class citizens in Haskell, and it's very hard to pass
them around, manipulate them and compute with them without using
non-standard and awkward techniques.

> Which is more appropriate here?

Almost certainly data.  My rule of thumb is to only introduce a typeclass
once it becomes incredibly repetitive passing around the data explicitly.

Tom