From: furufuru@... (Ryo Furue)
Date: 2001-08-11T19:43:29+09:00
Subject: [ruby-talk:19517] Why not?: Assigning to self

Hi there,

I wanted to add a "bang" method to the Array class:

class Array
   def smooth!
      n = self.size
      res = Array.new
      (1..n-2).each { |i|
	 res[i] = (self[i-1] + 2.0 * self[i] + ...
      }
      #self.each_index { |i| self[i] = res[i] }
      self = res
   end
end

The line "self = res" gives an error

   smooth:17: Can't change the value of self
         self = res

So I resorted to the line which is commented out in the code above. 
But, why is it forbidden to assign to self?  I think that assigning to
self and throwing away the object originally referenced by self is
more efficient than modifying the object referenced by self and
throwing away the one referenced by "res".  Am I missing something?

Cheers,
Ryo