From: Joost Diepenmaat <joost@...>
Date: 2008-08-30T05:20:08+09:00
Subject: Re: Does Ruby optimize tail-call recursion?

Patrick Li <patrickli_2001@hotmail.com> writes:

> Hi,
> I'm wondering if Ruby 1.9 optimizes tail-call recursion?
> I've read some reports that say yes, and some that say no. Does anyone
> know?

I just compiled the ruby svn trunk with all defaults:

 ./ruby -v
ruby 1.9.0 (2008-08-30 revision 18932) [i686-linux]


 ./ruby -e 'def bla(); bla(); end; bla()'
-e:1:in `bla': stack level too deep (SystemStackError)
        from -e:1:in `bla'
        from -e:1:in `bla'
        from -e:1:in `bla'
        from -e:1:in `bla'
        from -e:1:in `bla'
        from -e:1:in `bla'
        from -e:1:in `bla'
        from -e:1:in `bla'
         ... 7692 levels...
        from -e:1:in `bla'
        from -e:1:in `bla'
        from -e:1:in `bla'
        from -e:1:in `<main>'

So I guess the answer is: no, it does not optimize tail calls.

-- 
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/