From: "trans.  (T. Onoma)" <transami@...>
Date: 2004-12-03T08:20:34+09:00
Subject: Re: nested defs, what if...

On Thursday 02 December 2004 12:22 pm, Brian Schr旦der wrote:
| But where is this usefull? It seems only complicated and inefficent to me
| (Doesn't it create a new instance method on each call?):
|
| class A
|   def a()
|     def b()
|       self
|     end
|     self
|   end
| end
|     ==>nil
| A.new.b
| NoMethodError: undefined method `b' for #<A:0x402c0834>
|         from (irb):2
| A.new.a
|     ==>#<A:0x402a9cb0>
| A.new.a.b
|     ==>#<A:0x4029bad4>
| A.new.b
|     ==>#<A:0x40295864>

It is interesting. Does this mean that an _object_ could dynamically change 
the state of all objects of its class? I have to test....

class T
  def a
    def b
      puts "Hello"
    end
 end
end          => nil
t = T.new    => #<T:0x4032cb14>
t2 = T.new   => #<T:0x4032ae90>
t.b          => NoMethodError: undefined method `b' for #<T:0x4032cb14>
t2.b         => NoMethodError: undefined method `b' for #<T:0x4032ae90>
t.a          => nil
t.b          => nil
Hello  
t2.b         => nil
Hello

Yep. It sure does. This is very strange indeed. I wonder if you could write 
extentions in this way.

  class String
    def use(x)
      case x
      when :chars
        def chars
          self.split(//)
        end
      when :tab
        # ...
      end
    end
  end

Of course, you have to instantiate a string first. 

Well, it's an idea, but I don't think a very good one. In general I don't 
think this is useful, and would rather obfuscate code if actually used. I 
think what would be more useful is if such methods were local methods, like 
local variables:

  class A
    def a
      def b(x)
        x + 1
      end
      10.times{ |i| print b(i) }
    end
  end

  o = A.new
  o.b  => NoMethodError
  A.a  => 12345678910
  o.b  => NoMethodError

This would allow for embedded subroutines --much more useful.

T.