From: Logan Capaldo <logancapaldo@...>
Date: 2007-03-23T08:50:19+09:00
Subject: Re: #define alternative for Ruby

> set_default(var, val)
> -- if variable "var" is not defined (not existed) then assign value
> "val"
> 
require 'binding_of_caller' # google for this, you need call_stack
                            # or equiv for ruby >= 1.8.5
def set_default( var, val )
  Binding.of_caller do |b|
    eval("#{var} = #{val} unless #{var}", b)
  end
end

set_default( "a", "7" )