Re:Tail Call Recursion in Java with ASM (2023)
by knome on Sunday March 30, 2025 @03:32PM
(#43526835)
Sounds like a manual form of clojures recur function.
Re:Tail Call Recursion in Java with ASM (2023)
by 1932812267 on Sunday March 30, 2025 @03:49PM
(#43526996)
Clojure's loop/recur is specifically tail recursion like scala's tailrec or the optimization described in the blogpost. It doesn't use trampolines to enable tail calls that aren't tail recursion.
e.g.:
(defun func-a (x) (func-b (- x 34)) (defun func-b (x) (cond ((<= 0 x) x) ('t (func-a (-x 3))))
Because func-a and func-b are different (JVM) functions, you'd need an inter-procedural goto (i.e. a tail call) in order to natively implement this.
As an alternative, some implementations will use a trampoline. func-a and func-b return a _value_ which says what function to call (and what arguments) for the next step of the computation. The trampoline then calls the appropriate function. Because func-a and func-b _return_ instead of actually calling their sibling, the stack depth is always constant, and the trampoline takes care of the dispatch.