From: Yusuke ENDOH <mame@...>
Date: 2008-12-04T22:39:54+09:00
Subject: [ruby-core:20307] Re: Tail recursion?

Hi,

2008/12/4 Robert Dober <robert.dober@gmail.com>:
> Hi list
>
> I was just having some real fun with the 191p2 and somehow I was sure
> that tail recursion would be optimized away, but alas....
> I than searched the list for any information on that and did not find anything.
> Did I only dream or am I correct in assuming that Ruby1.9 will
> eventually optimize tail recursions?


YARV itself implements tail call optimization, but the feature is currently
disabled by default.  I guess this is because, if it is enabled,
- stack trace will change (and become harder to read), and
- set_trace_func cannot hook an event of method return.

But I also want tail call optimization in some cases.  I think a new method
call syntax or feature may be needed to declare that the call is tail call
and should be optimized.  For example, how about Method#tail_call:

  def foo
    ...
    method(:foo).tail_call
  end

-- 
Yusuke ENDOH <mame@tsg.ne.jp>