Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.ruby > #3112

Re: Tail Call Optimization (Tail Recursion)

Show all headers | View raw

7stud -- wrote:

> Terry Michaels wrote in post #993440:
> > I did some googling to find out if Ruby supports tail call optimization,
> > as I wanted to write tail-recursive functions. All posts I found
> > indicated that 1.9 supports this, but it is not enabled by default.
> > However, all those posts were about two years old, so I'm wondering what
> > is the current situation: do I still need to upgrade to 1.9 to get that
> > capability? Or is there something in 1.8 I can enable?
> 
> Couldn't you test that by creating two recursive functions: one with a 
> tail call and one without, and then benchmarking them?

def fib n, a = 0, b = 1
  if n == 0
    b
  else
    a, b = b, a + b
    fib n - 1, a, b
  end
end

1.upto(9){|n|
  p [n, fib(n)]
}

p fib( 50_000 )

  ==>

[1, 1]
[2, 2]
[3, 3]
[4, 5]
[5, 8]
[6, 13]
[7, 21]
[8, 34]
[9, 55]
try4.rb:23:in `fib': stack level too deep (SystemStackError)
        from try4.rb:23:in `fib'
        from try4.rb:31


irb(main):004:0> VERSION
=> "1.8.7"

Back to comp.lang.ruby | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Tail Call Optimization (Tail Recursion) Terry Michaels <cmhoward@frigidcode.com> - 2011-04-18 00:59 -0500
  Re: Tail Call Optimization (Tail Recursion) 7stud -- <bbxx789_05ss@yahoo.com> - 2011-04-18 12:29 -0500
    Re: Tail Call Optimization (Tail Recursion) "WJ" <w_a_x_man@yahoo.com> - 2011-04-18 18:10 +0000
      Re: Tail Call Optimization (Tail Recursion) Louis-Philippe <default@spiralix.org> - 2011-04-18 15:40 -0500
        Re: Tail Call Optimization (Tail Recursion) "WJ" <w_a_x_man@yahoo.com> - 2011-04-18 22:27 +0000
          Re: Tail Call Optimization (Tail Recursion) Louis-Philippe <default@spiralix.org> - 2011-04-19 07:28 -0500
            Re: Tail Call Optimization (Tail Recursion) "WJ" <w_a_x_man@yahoo.com> - 2011-04-20 04:12 +0000
              Re: Tail Call Optimization (Tail Recursion) "WJ" <w_a_x_man@yahoo.com> - 2011-04-20 04:30 +0000
                Re: Tail Call Optimization (Tail Recursion) Robert Klemme <shortcutter@googlemail.com> - 2011-04-20 06:37 -0500
        Re: Tail Call Optimization (Tail Recursion) Vincent Manis <vmanis@telus.net> - 2011-04-18 19:41 -0500
          Re: Tail Call Optimization (Tail Recursion) Steve Klabnik <steve@steveklabnik.com> - 2011-04-18 20:42 -0500
            Re: Tail Call Optimization (Tail Recursion) Vincent Manis <vmanis@telus.net> - 2011-04-18 21:51 -0500
              Re: Tail Call Optimization (Tail Recursion) Michael Edgar <adgar@carboni.ca> - 2011-04-18 22:12 -0500
              Re: Tail Call Optimization (Tail Recursion) Steve Klabnik <steve@steveklabnik.com> - 2011-04-19 08:48 -0500
                Re: Tail Call Optimization (Tail Recursion) Brian Candler <b.candler@pobox.com> - 2011-04-19 08:56 -0500
                Re: Tail Call Optimization (Tail Recursion) Steve Klabnik <steve@steveklabnik.com> - 2011-04-19 10:07 -0500
  Re: Tail Call Optimization (Tail Recursion) Steve Klabnik <steve@steveklabnik.com> - 2011-04-18 12:39 -0500

csiph-web