Discussion: Optimizing binary ops where one input is size 1

[DavisVaughan]

I think that eventually it would be useful to optimize the binary functions that currently recycle to a common size to instead only check for a common size and leave size 1 inputs un-recycled.

This issue should serve as a place to collect functions that could potentially benefit from this:

• [ ] vec_in(needles, haystack)
• [ ] vec_match(needles, haystack)
• [ ] vec_compare(x, y)
• [ ] vec_equal(x, y)

[DavisVaughan]

Slice assignment such as vec_slice(x, is_na) <- 0

[hadley]

I think we should try #49 before going down this path