[Bug-kawa] [bug #39606] tail calls not performed for top-level functions

[Per Bothner]

Update of bug #39606 (project kawa):

                  Status:                    None => Wont Fix               
             Assigned to:                    None => bothner                

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Follow-up Comment #1:

If works if you use the --full-tails option when starting up Kawa:
bash$ java -jar kawa-1.13.jar --full-tailcalls

See http://www.gnu.org/software/kawa/Compatibility.html and
http://www.gnu.org/software/kawa/Options.html#Options-for-compiling-and-optimizing

Otherwise when using the default calling convention we're limited by JVM (for
now at least).  The Kawa compiler will optimize away the most common kinds of
tail-calls, including (self-)tail-recursion, and some kinds of mutual
tail-recursion.  For example:

bash$ bin/kawa --debug-dump-zip
#|kawa:1|# (define e? (let () (define (e? x) (if (zero? x) #t (o? (- x 1)))) 
(define (o? x) (if (zero? x) #f (e? (- x 1)))) e?))
#|kawa:2|# (e?  10000)
#t

We can do better when the JVM gets native tail-call optimization.  Maybe Java
9 - if we're lucky - or enough people demand it.

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