And since I'm in a timing mood, here's the times for optional args:
(time (repeat 1000000 ((fn (a (o b 3)) (list a b)) 1 2)))
Arc 3.1 time: 1828 msec.
ar time: 1814 msec.
Nu time: 1554 msec.
So, it does make a difference that Nu uses plain lambdas, rather than complex fns! Now I just need to get apply to be faster.
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On a related note: racket-set! is slow. Using racket-let or Arc's let is faster, by a fairly significant amount. So I'll be changing my compiler so it doesn't use mutation.
