From: Phrogz <gavin@...>
Date: 2006-11-28T14:05:04+09:00
Subject: Re: find index of first non zeo value in array

Devin Mullins wrote:
> James Edward Gray II wrote:
> > I believe there has been talk in the past of having index() take a
> > block for matching.
> Meh... talk schmalk...
>
> class Array
>    alias orig_index index
>    def index(*args)
>      return orig_index(*args) unless block_given?
>      (0...length).each do |i|
>        return i if yield self[i]
>      end
>      nil
>    end
> end

Hrm, I assumed that using #each_with_index would be speedier, since
there would be no Ruby call to the #[] method of the array for each
iteration. Instead, it's much slower:

class Array
    alias orig_index index

    def index1(*args)
      return orig_index(*args) unless block_given?
      (0...length).each do |i|
        return i if yield self[i]
      end
      nil
    end

  def index2( *args )
    return orig_index(*args) unless block_given?
    each_with_index{ |value,index| return index if yield value }
    nil
  end
end

require 'benchmark'
N = 1000
a = (1..1000).to_a
Benchmark.bmbm{ |x|
  x.report( '0...length' ){
    N.times{ |i| a.index1{ |v| v==i } }
  }

  x.report( 'each_with_i' ){
    N.times{ |i| a.index2{ |v| v==i } }
  }
}

#=> Rehearsal -----------------------------------------------
#=> 0...length    2.060000   0.030000   2.090000 (  2.333379)
#=> each_with_i   3.340000   0.050000   3.390000 (  3.727040)
#=> -------------------------------------- total: 5.480000sec
#=>
#=>                   user     system      total        real
#=> 0...length    2.060000   0.020000   2.080000 (  2.286168)
#=> each_with_i   3.350000   0.040000   3.390000 (  3.716824)