From: cnb <circularfunc@...>
Date: 2008-09-08T11:53:56+09:00
Subject: Ruby tailcall optimizes?

Hmm this was a nice surprise. it seems Ruby does tailcall-
optimization? One up for Ruby on Python.

Is there a way to have optional arguments in Ruby? Then I could make
it one function instead of wrapping them.

irb(main):011:0> fact(12000)
fact(12000)
1201858406751094813215537862229...
irb(main):012:0> fac(12000)
fac(12000)
SystemStackError: stack level too deep
	from c:/ruby/Progs/blandat/learn.rb:34:in `fac'
	from c:/ruby/Progs/blandat/learn.rb:34:in `fac'
	from (irb):12
irb(main):013:0>


def fact(n)
    def f(n, acc)
        if n > 0
            then f(n-1, n*acc)
            else acc
        end
    end
    f(n, 1)
end

def fac(n)
    if n > 0
        then n * fac(n-1)
        else 1
    end
end