From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2011-06-03T01:51:59+09:00
Subject: Re: CORE - Replace "if __FILE__ == $0" with "executed?"

On Thu, Jun 2, 2011 at 6:34 PM, Chad Perrin <code@apotheon.net> wrote:
> On Thu, Jun 02, 2011 at 10:51:46PM +0900, Peter Zotov wrote:
>>
>> It failed because __FILE__ is not a constant: it is a special lexical
>> construct which is replaced by just a string containing the filename at
>> the point of _loading_ the file, i.e. even before the execution begins.
>> You simply cannot access it in any way after the file was loaded.
>>
>> You can still implement it this way (note that it may not work on
>> implementations other
>> than MRI):
>
> [snip]
>
> This seems to work just fine:
>
>    module Kernel
>      def executed?
>        __FILE__ == $0
>      end
>    end
>
>    if executed?
>      puts 'awesomesauce'
>    else
>      puts 'failsauce'
>    end
>
> What am I missing in the constraints of the request?

He wants to have the definition of the executed? method in a different
file, which gets required in his main file, and the problem is that
__FILE__ then it's evaluated to the name of the other file, not the
main file.

A solution, which I don't know if it feels clean enough would be to
pass that to the method:

#executed.rb
module Kernel
  def executed? file=__FILE__
    file == $0
  end
end

#main.rb
require 'executed'
if executed? __FILE__
  puts "Executed"
else
  puts "Loaded"
end

$ ruby main.rb
Executed
$ ruby -rmain -e ""
Loaded


Jesus.