There are two thinks to sort out: a) add left/right folds, b) add strict
folds.
I therefore propose to:
a) add foldrWithKey and foldlWithKey to IntMap, make foldWithKey
deprecated and synonymous for foldrWithKey.
+1
b) add foldl and foldr to Set and IntSet, make fold deprecated
and synonymous to foldr.
+1
c) add strict variants of left and right folds, namely
Data.Map, Data.IntMap: foldlWithKey' foldrWithKey'
Data.Set, Date.IntSet: foldl', foldr'
+1
Some issues:
- should we really rename fold -> foldr? Maybe we could cla
that fold and foldWithKey are right folds and add only
foldl and foldlWithKey.
I'd prefer to rename. We need to keep the old version around for a long time though, with a DEPRECATED pragma encouraging people to upgrade.
- should we really deprecate fold and foldWithKey? It could break
a lot of code.
I think so. Give people a year or so to move over.
- adding foldl, foldr, foldl' and foldr' to Set and IntSet is going to
cause a lot of trouble because of shadowing. Maybe some better name?
On the other hand, these are the "right" names.
I think we should go with the "right" names. I think many modules already import these modules qualified due to other name clashes (as they should). We should encourage proper use of namespaces to resolve name clashes. Breakages can be resolved by putting a upper version bound on containers in the .cabal file of the broken library.
-- Johan