Is this actually double dispatch? Visitor is a pattern that can be used for double dispatch, but I only count one guaranteed dispatch here. I'm not convinced t

Is this actually double dispatch? Visitor is a pattern that can be used for double dispatch, but I only count one guaranteed dispatch here. I'm not convinced that folks here saying, "We just us pattern matching like functional programming does" actually know how modern functional programming does this. From the perspective of runtime overhead and code size, this approach is very similar to recursion-schemes. Where RS excels over this approach is not in the use of pattern matching, but in the fact that it can reuse the functor structure to not even have to write the descending algorithm; it comes for free as part of your fixpoint functor.