Right you are. Ugh. I'll need to rethink this.
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`:
https://github.com/haskell/containers/pull/192
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).
--
RF