mapM /= traverse?

Simon Marlow marlowsd at
Tue May 12 15:58:57 UTC 2015

On 12/05/2015 15:26, Edward Kmett wrote:
> On Tue, May 12, 2015 at 3:58 AM, Simon Marlow <marlowsd at
> <mailto:marlowsd at>> 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.

Ok good, so it looks like the answer is "we could change it, but 
benchmark first".  I can do that.  Thanks!


More information about the Libraries mailing list