From: Robert Dober <robert.dober@...>
Date: 2007-03-01T21:02:28+09:00
Subject: Re: default passed block for method

On 3/1/07, Niko <niko@kingtong.org> wrote:
> dblack@wobblini.net wrote:
> > Hi --
> >
> > On Thu, 1 Mar 2007, Niko wrote:
> >
> >>
> >> Hi all,
> >>
> >> I'm trying to define the missing block given in the context of the
> >> method to avoid the block_given? test on each iteration for yield call.
> >>
> >> def self.list_of_relationships(relations, source)
> >>   # missing_block_that_yield_would_call = lambda { || true } unless
> >> block_given?
> >>   relations.map do |relation|
> >>     if yield(peer = relation.send(source))
> >>       [peer.display_name, peer.id]
> >>     end
> >>   end.compact
> >> end
> >
> > You would want to do:
> >
> >   def self.list(relations,source,&block)
> >     block ||= lambda { true } # no need for empty ||
> >     relations.map do |relation|
> >       if block.call(peer = ....
> >
> > etc.  You'd have to do some benchmarks to find out whether the
> > slowdown from call is worse than the slowdown from block_given?.
> >
> >
> > David
> >
>
> it works like a charm
> i'll do some benchmarks to check the slowdown
>
they are bad unfortunately, I would not have thought of it, great pointing at
that David.
========================================================
require 'benchmark'

def a1
	return true unless block_given?
	yield
end
def a2 &blk
	blk ||= proc{true}
	blk.call
end


    Benchmark.bmbm do |x|
      x.report("block_given?") {
      	424242.times do
			a1 { 'hi' }
			a1
      	end
      	 }
      x.report("&blk")  {
      	424242.times do
			a2 { 'hi' }
			a2
		end
      	  }
    end
--------------->

Rehearsal ------------------------------------------------
block_given?   1.280000   0.000000   1.280000 (  1.310912)
&blk           7.060000   0.020000   7.080000 ( 10.477620)
--------------------------------------- total: 8.360000sec

                   user     system      total        real
block_given?   1.280000   0.000000   1.280000 (  1.284248)
&blk           7.090000   0.010000   7.100000 (  9.274008)

==================================================================
> thanks for the help
>
>
>


-- 
We have not succeeded in answering all of our questions.
In fact, in some ways, we are more confused than ever.
But we feel we are confused on a higher level and about more important things.
-Anonymous