complex derivatives

[Roger-luo]

there are two different kind of derivatives for complex valued function, one the df/dz, the other is the df/d conj(z). It'd be nice to support both.

[willtebbutt]

@Roger-luo is this issue resolved from your perspective?

[Roger-luo]

I'm not sure, how do you calculate the complex derivative currently? I haven't been following recent updates.

[willtebbutt]

julia> FiniteDifferences.grad(central_fdm(5, 1), abs2 ∘ cos, 1.0 + 1.0im)
(-0.9092974268258326 + 3.6268604078472806im,)

[Roger-luo]

yeah I think I was thinking about using two interface (one for df/dz the other for df/dconj(z), this is good on my side now. I'll post other issues if I find anything, thanks!