From: Bulat Ziganshin <bulatz@...>
Date: 2003-02-27T22:16:09+09:00
Subject: Re: Return Values of [] for Array, Hash,... (ruby 1.6.8)

Hello Brian,

Thursday, February 27, 2003, 4:06:41 PM, you wrote:

>> > ALL TYPES ARE HANDLED SAME WAY.
>> This is completely clear. Question (NOT TO BE DISCUSSED NOW) is, 
>> which;), why;), couldn't it be done better;), ... ?
>> 
>> To make the problem clearer:
>> def fu, h, key, &b, o 
>>       e = h[key]
>>       b.call(e,o) # should modify e
>> end
>> If e is of type Integer (for example), h[key] will not be modified),
>> if e is of type Object, h[key] will be modified.

BC> But Integer is also an Object (it's a subclass). There is no inconsistency.
BC> Whatever function 'b' does, it is unable to change e. It can make method
BC> calls to the object referenced by e, though, which may in turn change its
BC> state if it contains instance variables.

BC> Integers do not contain instance variables, and therefore there is no state
BC> to change.

i can add that, to be exact, some types has methods which change internal
object state (whose names ends with "=" or "!", typically) and some types
don't have such methods. someone can create unmodifable types, it's easy:

class Persistent
end

class Persistent2
  attr_reader :x,:y
  def initialize(a,b)
    x=a
    y=b
  end
end

-- 
Best regards,
 Bulat                            mailto:bulatz@integ.ru