Yes, they do. In particular, the zip can only fuse with one of the two lists so the Ints could be unboxed, or fusion optimizations could happen with the list folded over, but not both. The fold_WithIndex function can manage both at once. That said, I think there have been some pretty good arguments against adding these, or at least against adding them with these names.

On Oct 22, 2014 3:13 PM, "Ganesh Sittampalam" <ganesh@earth.li> wrote:
On 16/10/2014 18:14, David Feuer 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.

Do these do anything better than just adding indicies first with the standard zip [0..] idiom?

Cheers,

Ganesh

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