[gruseom]

I don't think Smalltalk has code=data. It has object-based metaprogramming, i.e. the code that you write turns into objects that you can write other code to manipulate at runtime. But perhaps that's a distinction without a difference? I don't have enough experience with Smalltalk to say.

I was expecting someone to suggest that stack-based languages are fundamentally different from tree-based ones.