Allow non-scalar arguments to atan2 when dimensions match

[imacg]

Fix atan2 to allow arguments with the same dimensions and remove duplicate code.

[sharkdp]

Great work, thank you very much!!

I think we can remove the old lift2 function (it is not exported and not used anywhere) and rename your new implementation from lift2' to lift2.

[imacg]

Thanks. Sorry for missing the dead function.

[sharkdp]

Thank you!

[sharkdp]

Oh - my bad: I should have checked it more thoroughly before merging.

Your changes are great for max2, min2, and modulo, but atan2 has to be handled differently, I think.

Conceptually, atan2(y, x) is like atan(y/x). So we want y and x to have compatible units, however: the result is dimensionless!

[sharkdp]

Unfortunately, we didn't have any tests for atan2. We should add something like this (somewhere around here):

    test "atan2" do
      almostEqual' (scalar (Math.pi / 4.0)) ((100.0 .* centi meter) `atan2` (1.0 .* meter))

[imacg]

I've fixed the issue and added a few tests. Unfortunately since I deleted my branch before your comment this PR isn't tracking my changes; are you able to edit this PR or should I open a new one?

Thanks for your patients.

[sharkdp]

Please open a new PR. Thank you very much!