Proposal: Add foldrWithIndex and foldlWithIndex to Data.List

[Edward Kmett]

I'm a pretty strong -1 on moving foldrWithIndex into Data.Foldable.

Why?

The only index Foldable can provide is an ordinal index starting at 0.

The one folks _expect_ in many cases from Map k, IntMap and the like is the
key.

This introduces a huge source of potential confusion and new name conflicts
for marginal benefit.

-Edward

On Thu, Oct 16, 2014 at 1:21 PM, David Feuer <david.feuer at gmail.com> wrote:

> Actually, that proposal is firmly in the past. Let's *move* foldrWithIndex
> and foldlWithIndex from Data.Sequence to Data.Foldable!
>
> On Thu, Oct 16, 2014 at 1:14 PM, David Feuer <david.feuer at gmail.com>
> wrote:
>
>> These functions can be lifted pretty much straight out of Data.Sequence.
>> In particular, foldrWithIndex makes for a particularly nice expression of a
>> fusing findIndices function, as is present in Data.Sequence.
>>
>
>
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