>2. Tail recursion doesn't really make much of a difference for walking trees, which is recursive, but (mostly) not tail recursive. Non-strictness helps here m

>2. Tail recursion doesn't really make much of a difference for walking trees, which is recursive, but (mostly) not tail recursive. Non-strictness helps here more than TCO in a strict language. >4. ADTs can be good or bad for describing ASTs. Once you enrich ASTs with semantics shared by all variants (such as source coordinates), inheritance can become a better fit than ADTs. Since this article was written we have better ways of augmenting/annotating ASTs. There's a lot of this out there, but here's one example: https://brianmckenna.org/blog/type_annotation_cofree https://brianmckenna.org/blog/type_annotation_cofree There are other alternatives that are like inheritance but with better reasoning properties as well. Finally tagless comes to mind. >I also generally find it better to explicitly annotate functions with types. This Haskeller whole-heartedly agrees for all the reasons stated.