I am sympathetic to the completeness argument, but I would prefer that
we not add more partial functions to base. Having foldl1 and foldr1 in
Foldable in the first place is something I consider a wart. Hopefully
we can remove them in the future.
Would it make sense to omit foldl1/foldr1/foldl1'/foldr1' entirely
from your explanation? Then it would be future-proofed against such
removal :)
Cheers,
George
On Mon, 21 Dec 2020 at 08:16, Viktor Dukhovni
Given that Foldable currently has:
- foldr and foldr' - foldl and foldl' - foldMap and foldMap'
and also has only:
- foldr1 - foldl1
it seems natural to ask whether there it should also have a strict variant of at least foldl1, since the non-strict variant has rather limited applicability, and users would/should in most cases want/use the strict `foldl1'` instead.
-- Viktor.
P.S. I just joined the list today, but noticed that coincidentally, there's already a recent dicussion of Foldable1, which rather overlaps with this question, and perhaps the partial `foldr1` and `foldl1` should be seen as deprecated, once a suitable class of non-empty containers provides total variants. But perhaps on the other hand, given that the partial functions already exist, perhaps adding the strict companions is warranted?
I am asking because I am writing some expository prose for Data.Foldable, to go at the bottom of the document, structurally along the lines of what I contributed for Data.Traversable, but with a fairly different focus. The goal is draw careful distinctions between strict recursive and lazy corecursive reductions, explaining their proper usage and typical implementations. The "missing" `foldl1'` was something I ran into while working on part of the writeup. _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries