[aidenn0]

> The part that is missing is the stack. So I wonder what would happen if you let them step through while showing the stack state at every point. This would clue them in immediately that there is nested control flow.

I saw so many of my peers needlessly confused by a pedagogy that insists that the call stack is an implementation detail and thus does not belong in a CS class.

[Someone]

Nitpick: the call stack is an implementation detail. It is a way to implement call frames.

Because that implementation doesn’t handle functions returning closures that depend on the call frame, something that is very common in modern languages, I think we should teach call frames first.

Starting with a call stack makes understanding how closures work later unnecessarily hard.

That also is what SICP does. It starts with call frames in chapter 3 (https://mitp-content-server.mit.edu/books/content/sectbyfn/b...) and only in chapter 5 introduces stack frames when discussing how to implement recursion on register machines (https://mitp-content-server.mit.edu/books/content/sectbyfn/b...)

[aidenn0]

> Nitpick: the call stack is an implementation detail. It is a way to implement call frames.

Sorry, I was unclear that it was the second half of the implication I disagreed with. I never had the pleasure of a SICP based class, but I did eventually learn the concept of closures (though never in a CS class). Many of my peers were flummoxed by recursion and I personally believe that intentionally avoiding discussion of a call stack was poor pedagogy (possibly because I leaned on my understanding of it when I first learned recursion) that unnecessarily caused people to drop out long before they would ever encounter closures.

> Because that implementation doesn’t handle functions returning closures that depend on the call frame, something that is very common in modern languages, I think we should teach call frames first.

I guess I'm showing my age. Pascal, C, C++ and Java (which at the time lacked not only closures, but also generics) were the only languages I encountered in my CS classes (there was an optional upper-level survey of languages class that I didn't take). I will, however, stand by my general sentiment that there are a large class of people that learn better by learning a concrete example and then generalize to the abstract, and those students were poorly served by the pedagogy I encountered.