> I’m not certain, but I am pretty sure tail call optimization includes generic tail call elimination.
I believe they're related, but not the same thing.
> I do not know if the above is included in what clojure does for tail calls, recursive or not, but on the JVM the elimination of those calls can and does have an impact.
As far as I know the JVM doesn't allow a program to arbitrarily modify the stack, so any support would need to be baked into the JVM itself, which it might be now, but I'm not finding any indication that it is. The `loop`/`recur` construct essentially compiles to a loop in the Java sense (to my understanding), so it is as efficient as a recursive loop with TCO. The more general tail-call elimination likely isn't possible on the JVM, but you're correct that it would likely result in a speed up.
All of this is sort of besides the point: I don't think there's much in terms of higher-order functions (which is an extremely broad category of things) that you can't do in Clojure just because it lacks TCO. At least no one has been able to give me an example or even address the point directly. Speed is not really what I'm referring to.
If you program purely and represent "state" as a function
s -> (a,s)
Then the JVM bites you the moment you naively abstract over that. You end up having to manually "compile" stuff like traversing a list with a stateful update. For example, Scala's pure FP ecosystem is full of specialized functions for state due to this.
I believe they're related, but not the same thing.
> I do not know if the above is included in what clojure does for tail calls, recursive or not, but on the JVM the elimination of those calls can and does have an impact.
As far as I know the JVM doesn't allow a program to arbitrarily modify the stack, so any support would need to be baked into the JVM itself, which it might be now, but I'm not finding any indication that it is. The `loop`/`recur` construct essentially compiles to a loop in the Java sense (to my understanding), so it is as efficient as a recursive loop with TCO. The more general tail-call elimination likely isn't possible on the JVM, but you're correct that it would likely result in a speed up.
All of this is sort of besides the point: I don't think there's much in terms of higher-order functions (which is an extremely broad category of things) that you can't do in Clojure just because it lacks TCO. At least no one has been able to give me an example or even address the point directly. Speed is not really what I'm referring to.