map which returns tuples of vectors would also be nice

[pdeffebach]

Thanks for making Unzip. I appreciate it.

My main use-case for unzip, though, is returning a tuple of vectors from map rather than a vector of tuples. Would this be possible to add to Unzip?

[bramtayl]

I think it should work already! You could even use Iterators.map for even more performance. Do you have an example?

[pdeffebach]

No, I mean a version of map that does it automatically, i.e.

julia> function maptup(f, args...)
           out = Tuple.(map(f, args...))
           unzip(out)
       end
maptup (generic function with 1 method)

julia> a, b = maptup(rand(10)) do x
           (x + 1, x - 1)
       end
([1.4738536202542285, 1.865283772114408, 1.1367533401175127, 1.680097789641812, 1.6853770322606707, 1.6453793708506164, 1.8524757820092266, 1.4489005984590795, 1.693449394611504, 1.8753358407742735], [-0.5261463797457715, -0.134716227885592, -0.8632466598824873, -0.3199022103581881, -0.3146229677393293, -0.35462062914938364, -0.14752421799077342, -0.5510994015409205, -0.3065506053884961, -0.12466415922572649])

If people are so concerned about performance in the julia issue, then better to attack the problem directly by avoidingthe intermediate allocation of out.

This is my main use-case for wanting unzip, so maybe asking for unzip is a bit of an x-y problem

[bramtayl]

Right, this should work out of the box:

@btime a, b = unzip(Iterators.map(rand(10)) do x
    (x + 1, x - 1)
end)
# 216.867 ns (4 allocations: 720 bytes)

[pdeffebach]

oh, cool.

One final motivation for having this in its own function (beyond saving typing), is that this could potentially also be a map! version of this as well. Where you fill in elements of a named tuple. This can probably be it's own package though.

[bramtayl]

Hmm, actually, I think that's also possible using some of the internals of this package.

using Unzip: Rows
vectors = Rows(((Vector{Int}(undef, 10), Vector{Int}(undef, 10))))
map!(x -> (x - 1, x + 1), vectors, 1:10)

I suppose I could write up a docstring for Rows and export it?