Why is there no optimization for Java tail recursion?

302    Asked by OtaAzuma in Java , Asked on Oct 12, 2022

From what I have read: The reason is because it is not easy to determine which method will actually be called as we have inheritance.

However, why doesn't Java at least have tail-recursion optimization for static methods and enforce proper way to call static methods with the compiler?

Why doesn't Java have any support at all for tail-recursion?

I am not sure if there is any difficulty here at all.

Regarding the suggested duplicate, as explained by Jörg W Mittag1:

The other question asks about TCO, this one about TRE. TRE is much simpler than TCO.

Also, the other question asks about what limitations the JVM imposes on language implementations that wish to compile to the JVM, this question asks about Java, which is the one language that is not restricted by the JVM, since the JVM spec can be changed by the same people who design Java.

And lastly, there isn't even a restriction in the JVM about TRE, because the JVM does have intra-method GOTO, which is all that's needed for TRE


Answered by Owen Welch

Java doesn't have optimization for Java tail recursion for the same reason most imperative languages don't have it. Imperative loops are the preferred style of the language, and the programmer can replace tail recursion with imperative loops. The complexity isn't worth it for a feature whose use is discouraged as a matter of style.


This thing where programmers want to sometimes write in a FP-style in otherwise imperative languages only came into vogue in the last 10 years or so, after computers started scaling in cores instead of GHz. Even now, it's not that popular. If I suggested replacing an imperative loop with tail recursion at work, half the code reviewers would laugh and the other half would give a confused look. Even in functional programming, you generally avoid tail recursion unless other constructs like higher-order functions don't fit cleanly.



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