From: "David A. Black" <dblack@...>
Date: 2004-12-08T23:12:56+09:00
Subject: Re: Using yield

On Wed, 8 Dec 2004, Robert Klemme wrote:

> If the other method (Fixnum#times in my example) would do different
> yielding.  Hm...  I think I should redefine my set:
>
> 14:52:25 [09_Public]: ruby yield-vs-block.rb
>                          user     system      total        real
> yield                 0.265000   0.000000   0.265000 (  0.263000)
> yield_star            0.766000   0.000000   0.766000 (  0.778000)
> block                 0.109000   0.000000   0.109000 (  0.124000)
> 14:52:58 [09_Public]: cat yield-vs-block.rb
>
> require 'benchmark'
> include Benchmark
>
> REP = 100000
>
> def bl_yield(n)
>  n.times {|i| yield i}
> end
>
> def bl_yield_star(n)
>  n.times {|*i| yield *i}
> end
>
> def bl_fwd(n,&b)
>  n.times(&b)
> end
>
> bm(20) do |b|
>  b.report("yield") do
>    bl_yield(REP) {|i| i + 1}
>  end
>
>  b.report("yield_star") do
>    bl_yield_star(REP) {|i| i + 1}
>  end
>
>  b.report("block") do
>    bl_fwd(REP) {|i| i + 1}
>  end
> end
>
> Uh, even worse performance for "yield *i". *shudder*  But not really
> unexpected.  One more reason to use &b for forwarding.

I think my vague concern about argument parsing has to do with the
question of who gets to decide.  There might be a case where for some
reason you wanted to do:

   def some_method(n)
     n.times {|*i| yield i}
   end

or something weird like that... but I guess that takes us away from
exact equivalence with &b, since now I'm not just passing the args to
yield one at a time as they come.


David

-- 
David A. Black
dblack@wobblini.net