On Mon, Apr 8, 2013 at 7:59 AM, Joachim Breitner <mail@joachim-breitner.de> wrote:

Hi,

I believe one problem with non-linear patterns would be that the
compiler has to figure out what notion of equality you want here. An
obvious choice is (==), but the Eq instances might not do what you want.
Using pattern guards or view patterns explicates this choice.

What other types of equality would be possibilities?

Also, for some history, this was discussed a while back: http://www.mail-archive.com/haskell@haskell.org/msg03721.html

Erlang programmers have this feature without shooting themselves in the foot too often. That said, I'm happy without it.

Tom