[Haskell-cafe] data/newtype vs. class

[Tom Ellis]

On Mon, Jun 16, 2014 at 08:54:30PM +0200, martin wrote:
> Can someone give me some guidance, when to use classes and when to use
> data?  Are the two concepts interchangeable in some scenarios?

The simplest way of answering this which is mostly correct is:

    use data