From: jmichel@...2.institut.math.jussieu.fr (Jean Michel)
Date: 2001-08-16T07:32:54+09:00
Subject: [ruby-talk:19850] Re: Why not?: Assigning to self

>On Tuesday 14 August 2001 09:38 am, Dave Thomas wrote:
>
>> Perhaps if we could see an actual example of where this is needed we
>> could discuss this better. I know there was some talk a while back of
>> some code that handled (I think) archives or somesuch. Could be see
>> the code for this so we could think about it.
>

I came upon  something which is perhaps an exemple  where one might want
to change self, or perhaps just I  did not find the right way to achieve
my aim.

I came upon a situation which could be handled nicely by adding a couple
of  methods to  the class  Range (I  will elaborate  the situation  in a
further message if people are interested):

Class Range
  def shrink_up
    @begin+=1
  end  
  def shrink_down
    @end-=1
  end
end

Well,  this  does  not  work  since  begin  and  end  are  not  writable
attributes (nor attributes at all, in fact). The next try would be :)

Class Range
  def shrink_up
    self=(begin+1..end)
  end  
  def shrink_down
    self=(begin..end-1)
  end
end

Here I am stuck: how to add such  methods to range or to a class derived
from  range? It  seems that  by design  ranges, contrary  to some  other
classes  like strings  or arrays,  are  immutable. Is  this a  conscious
design decision which has advantages, or did it happen by chance?

Best regards,
  Jean Michel