Discussion: reconsider lens-like exports from containers

rf at rufflewind.com rf at rufflewind.com
Wed Apr 27 07:19:02 UTC 2016

On Tue, Apr 26, 2016, at 15:03, David Feuer wrote:
> Way back when, Shachaf Ben-Kiki suggested an efficient implementation
> of `at` for Data.Map in
> https://mail.haskell.org/pipermail/libraries/2013-May/019761.html but
> that was never approved for inclusion.

Funny thing, I just tried doing that not to long ago with `at`:


In the end, the results were mixed.  It was a small optimization in some
situations, and a moderate pessimization in others (esp. when the
Functor becomes too complex for GHC to optimize).


More information about the Libraries mailing list