Re: [Haskell-cafe] Things to avoid (Was: Top 20 ``things'' to know in Haskell)

Iavor Diatchki writes in response to Thomas Jäger

Literal patterns need equality: f 2 = e is like: f x | x == 2 = e

These do not force the 'Num' class to be a superclass of 'Ord' or 'Eq'. If 'Num' was not a superclass of 'Eq', whenver you used a literal pattern there would be an extra constraint that there should be equality on the corresponding type.

You mean of course that Eq is a superclass of Num, not the reverse. Anyway, I always hated this, especially working with functional objects for which I had some arithmetic defined... Jerzy Karczmarczuk