Fwd: Proposal: Implement minimumOn, maximumOn to mirror sortOn
Hello, I have a small proposal for review here: https://phabricator.haskell.org/D5110 I'd like to start the discussion on whether this is a useful/acceptable addition the core library. Thanks, - Gabriel
I personally have no strong objection here. Yes there is a Fairbairn
threshold argument to be had, but to be honest, we've already let that go
with sortOn, so consistency seems to be the better option.
I'm +1.
-Edward
On Mon, Oct 29, 2018 at 7:32 PM Gabriel Garcia
Hello,
I have a small proposal for review here: https://phabricator.haskell.org/D5110
I'd like to start the discussion on whether this is a useful/acceptable addition the core library.
Thanks, - Gabriel _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
Having the consistency with `sortOn` seems like a win, but the reason we have `sortOn` is that the implementation is not completely trivial. It has to be ever so slightly smart to reuse the projections when sorting. On the other hand, we have the definitions: minimumOn = minimumBy . comparing maximumOn = maximumBy . comparing It’s not obvious to me that this needs its own name instead of simply mentioning that `comparing` exists in the haddock documentation for `minimumBy` and `maximumBy`. Is it a foregone conclusion that we should maintain consistency with `minimum` and `maximum` on their result types? I consider these types mistakes and would have preferred to see `Maybe` involved. minimumOn :: (Foldable t, Ord b) => (a -> b) -> t a -> Maybe a I’m not sure why it makes sense to force ourselves into returning an imprecise exception in the empty list case. Best regards, Eric Mertens
I am -1 on this. These functions are built on top of foldl1. Consequently,
they are partial functions. The constraint on these is rightfully Foldable1
(possibly to be renamed to Semifoldable), which may one day reside in base.
Although we cannot go back in time and prevent the proliferation of partial
functions in base, we can avoid introducing more of them.
On Mon, Oct 29, 2018 at 8:09 PM Eric Mertens
Having the consistency with `sortOn` seems like a win, but the reason we have `sortOn` is that the implementation is not completely trivial. It has to be ever so slightly smart to reuse the projections when sorting.
On the other hand, we have the definitions:
minimumOn = minimumBy . comparing maximumOn = maximumBy . comparing
It’s not obvious to me that this needs its own name instead of simply mentioning that `comparing` exists in the haddock documentation for `minimumBy` and `maximumBy`.
Is it a foregone conclusion that we should maintain consistency with `minimum` and `maximum` on their result types? I consider these types mistakes and would have preferred to see `Maybe` involved.
minimumOn :: (Foldable t, Ord b) => (a -> b) -> t a -> Maybe a
I’m not sure why it makes sense to force ourselves into returning an imprecise exception in the empty list case.
Best regards, Eric Mertens _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries
-- -Andrew Thaddeus Martin
participants (4)
-
Andrew Martin -
Edward Kmett -
Eric Mertens -
Gabriel Garcia