Ok. I see. I already have everything in external C++ functions that returns a logLL for a set of free parameters. Can I use this as a custom logLL function in the model block?
Also, I’m figuring that simply doing everything by using std::complex won’t do the job, since I need a stan var type complex for it to work, right? Is that because of the autodiff? What exactly is the var type? And how will a complex var type variable look like?