step() slowness

[rust-itertools]

step() slowness

[bluss]

It's not really surprising, .step() is written for general iterators and uses .fuse() among other things (whose performance impediment is well known).

[palacaze]

Thanks for the explanation. I see now that step_by() is only implemented for ranges.
Should the performance implications be mentioned in the documentation, as a few iterators, such as interleave(), make use of Fuse internally?

[bluss]

It's not just fuse, it's a lot of stuff that needs to be covered. Every adaptor could have its own performance story explained.

Step could possibly be improved with specialization (also fuse-related specialization).

[bluss]

One prerequisite for making the best step iterator for slices (like Stride/StrideMut) is to have arith_offset as a stable function. Then specialization to let us do interesting specializations in itertools itself.

[bluss]

std has Iterator::step_by now. We can deprecate step() when it's stable.

[bluss]

Step has been deprecated in itertools 0.8