From: Aldric Giacomoni <aldric@...>
Date: 2009-11-20T03:35:11+09:00
Subject: Re: Re-opening an existing module and changing a method

Marnen Laibow-Koser wrote:
> 
> Looks fine to me.  Does old_sqrt actually return a Float or some other 
> numeric type?
> 
> Actually, why use type checking at all?  Why not change the condition to 
> use kind_of or simply test result.to_i - result == 0 ?
> 
Well.. Not that it's particularly meaningful, but here's my benchmark 
for that question:

require 'benchamrk'
num = 5.5
n = 5_000_000
Benchmark.bmbm do |x|
  x.report("kind_of?") { n.times do ; n.kind_of? Float ; end }
  x.report("is_a?")    { n.times do ; n.is_a? Float    ; end }
  x.report("to_i")     { n.times do ; n.to_i - n == 0  ; end }
end

Rehearsal --------------------------------------------
kind_of?   1.719000   0.000000   1.719000 (  1.720000)
is_a?      1.641000   0.000000   1.641000 (  1.642000)
to_i       2.750000   0.000000   2.750000 (  2.751000)
----------------------------------- total: 6.110000sec

               user     system      total        real
kind_of?   1.734000   0.000000   1.734000 (  1.735000)
is_a?      1.703000   0.000000   1.703000 (  1.720000)
to_i       2.688000   0.000000   2.688000 (  2.689000)

__________________

You know how metaprogramming is all about the self, according to Yehuda 
Katz's latest blog post? :) I, er, forgot to do self.sqrt ...

module Math
  alias_method :old_sqrt, :sqrt
  def self.sqrt x
    result = 5.5 #self.old_sqrt(x)
    if result.is_a? Float
      "sqrt(#{x})"
    else
      result
    end
  end
end


>> puts Math.sqrt(2)
=> sqrt(2)
>> puts Math.methods.find { |i| i[0..0] == "o"}
=> object_id

... So I'm not sure how to do an alias_method on a method that's got a 
"self." in front of it, I guess..
puts Math.methods.find { |i| i[0..0] == "o"}
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