On Tue, May 12, 2015 at 3:58 AM, Simon Marlow <marlowsd@gmail.com> wrote:

Yes, I'm not really concerned that mapM is a method of Traversable rather than just being an alias for traverse, but I'm wondering why we define it in the list instance rather than using the default.

We were pretty paranoid about introducing space or time regressions and didn't have a proof that we wouldn't introduce them by changing something there, so we left it alone.

-Edward