Non-intutive behaviour for getp and setp

[TorkelE]

So, with the latest update you cannot index structures directly for parameters, but instead have to use getp and setp. I understand that it make sense to split this into several steps for performance reasons, but stuff like:

getp(prob, k)(prob)

is both messy and confusing to the user. Furthermore, the performance cost (at least for small problems) is incredibly reliable.

Also, e.g. getp(oprob, p) really sounds like something that gets you the value of p in prob. Would it make sense to rename the current ones to something like:

k_getter = pgetter(prob, k)
k_setter = psetter(prob, k)

and then one can do

k_getter(prob)
k_setter(prob, 1.0)

Next, we could have getp and setp! which simply does what you want:

getp(prob, k)
setp(prob, k, 1.0)

something like this feels like a much more intuitive interface.

An alternative is the version where we permit indexing of prob.ps directly, so yo can do

prob.ps[k] # getp
prob.ps[k] = 1.0 # setp

[AayushSabharwal]

Closing since SciML/SciMLBase.jl#584 released in https://github.com/SciML/SciMLBase.jl/releases/tag/v2.21.0 enables .ps[p] syntax