If you’re interested in more feedback here are some thoughts :).
- I think it really is worth making the example of functors more explicit. Your example mentions it as a special case of completely different functions where one performs a runtime check, but there are also many other cases that people might naively think o using vectors of functions, i.e. polynomials, interpolations, rotation transformations e.t.c. for which functors are perfectly suited. Personally, I think the first question one should ask oneself before using a collection of functions, is if there is any way one could use a functor instead.
- there is a package called
FunctionWrapperWrappers.jl. I have no idea what it is used for, but if you do, perhaps this is also useful to mention?
Anyway it’s awesome that you do this, I have seen questions about vectors of functions appear quite a few times 
and not so many resources about the solutions