Opaque functions and fsolve / numerical methods

[compaqdrew]

How did you figure that out? I can't find a reference to "CAS functions" in the manual nor to the "#cas" statement (...directive?) I was able to turn up a few forum threads but mostly discussing syntax and not really any differences in the programming model or why to prefer one vs the other.

I also found FNROOT, which seems like a noncas version of fsolve. I guess it makes some sense to use like functions with like, but I'm fuzzy on how cas/noncas actually differ in their programming model or typesystem.

My intuition was that a numerical solver would want to operate on numbers and not symbolic representations, but it seems for fsolve this is not the case...