From: Joel VanderWerf <vjoel@...>
Date: 2006-02-18T14:49:37+09:00
Subject: Re: define_method fun

Patrick Ritchie wrote:
> Hi All,
> 
> I just setup the following in one of my classes, I'll let the code speak
> for itself:
> 
> ["<", "<=", ">", ">=", "==", "<=>"].each do |op|
>  define_method(op) { |comparison| eval "#{self.order} #{op}
> #{comparison.order}" }
> end
> 
> Ruby continues to impress me with it's ability to do so much in so few
> amazing readable lines of code.
> 
> Are their any good reasons not to declare my op methods this way? Is
> their an even more efficient way to achieve the same effect?

It helps to pull the eval out of the define_method:


module Order
  attr_reader :order
  def initialize order
    @order = order
  end
end

class EvalInside
  include Order
  ["<", "<=", ">", ">=", "==", "<=>"].each do |op|
    define_method(op) { |comparison| eval "#{self.order} #{op}
#{comparison.order}" }
  end
end

class EvalOutside
  include Order
  ["<", "<=", ">", ">=", "==", "<=>"].each do |op|
    eval "define_method(:#{op}) { |comparison| self.order #{op}
comparison.order }"
  end
end

require 'benchmark'

inside = []
outside = []
1000000.times do |i|
  order = rand(1)
  inside << EvalInside.new(i)
  outside << EvalOutside.new(i)
end

Benchmark.bmbm do |bm|
  bm.report("eval inside") do
    inside.sort
  end

  bm.report("eval outside") do
    outside.sort
  end
end


Rehearsal ------------------------------------------------
eval inside   17.280000   0.030000  17.310000 ( 18.088599)
eval outside   2.170000   0.010000   2.180000 (  2.254999)
-------------------------------------- total: 19.490000sec

                   user     system      total        real
eval inside   17.260000   0.010000  17.270000 ( 17.873053)
eval outside   2.150000   0.010000   2.160000 (  2.248230)


-- 
      vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407