From: Ryan Davis <ryand-ruby@...>
Date: 2008-02-07T14:16:14+09:00
Subject: Re: idiom I've not seen before


On Feb 6, 2008, at 20:04 , Rob Biedenharn wrote:

> You've found Symbol#to_proc
>
> That line is equivalent to:
>
> elements.sort_by {|e| e.send(:position) }.each

Buyer beware:

#!/usr/local/bin/ruby -w

# # of iterations = 10000
#                           user     system      total        real
# null_time             0.000000   0.000000   0.000000 (  0.001561)
# map                   0.880000   0.000000   0.880000 (  0.878500)
# to_proc               2.790000   0.000000   2.790000 (  2.799291)

# # of iterations = 100000
#                           user     system      total        real
# null_time             0.020000   0.000000   0.020000 (  0.013951)
# map                   8.730000   0.010000   8.740000 (  8.766693)
# to_proc              27.960000   0.030000  27.990000 ( 28.001288)

require 'benchmark'

class Symbol
   def to_proc
     Proc.new { |*args| args.shift.__send__(self, *args) }
   end
end

a = (1..100).to_a

raise "stupid" unless a.map { |n| n.to_s } == a.map(&:to_s)

max = (ARGV.shift || 1_000_000).to_i

puts "# of iterations = #{max}"
Benchmark::bm(20) do |x|
   x.report("null_time") do
     for i in 0..max do
       # do nothing
     end
   end

   x.report("map") do
     for i in 0..max do
       a.map { |n| n.to_s }
     end
   end

   x.report("to_proc") do
     for i in 0..max do
       a.map(&:to_s)
     end
   end
end