From: "Chr. Rippel" <chr_news@...>
Date: 2002-01-26T18:32:51+09:00
Subject: Re: Serious Array Bug in Ruby 1.6.6?

"William Djaja Tjokroaminata" <billtj@y.glue.umd.edu> wrote in message
news:a2sli3$7kf$1@grapevine.wam.umd.edu...
> Christoph,
>
> Thank you, thank you for summarizing it quite well.  For me with C/C++
> background, it is much easier to just say all Ruby references or variables
> are pointers (except the FixNum, True, etc.)  So basically Ruby only
> supports
>
>     ...
>     pointer = &(new (object));
>     vector a = new (n, pointer);
>
> and not
>
>     vector a = new (n, object);
>
> (excuse me if the syntax is wrong; I have not used C++ for a long time).
>
> Yes, the List class is exactly what I want.  I don't see why it is so
> inefficient, because the opposite is I still don't see the use of an array
> of pointers to the same object.  If it is so inefficient, why just don't
> provide it to the user: Array.new (n, obj) only works for obj of FixNum,
> True, Nil, etc.  On the other hand, if it is allowed for obj to be a Hash,
> then why not create multiple hashes instead of just a single hash.

All of these objects are very special - true,false and nil are the instance
of classes that implement the Singleton pattern - for example, cloning
and duping are a priori prohibited.  FixNums are actually not special
(in this respect) - they just apear this way.

----
class Fixnum
  attr_accessor :var
  alias __to_s to_s
  def to_s
    unless defined? @var
       __to_s
    else
      "#{__to_s} and @var = #{@var}"
    end
  end
  alias inspect to_s
  private :__to_s
end

L = Array.new (3,1)
p L
L[0].var= "a"
p L
----
[1, 1, 1]
[1 and @var = a, 1 and @var = a, 1 and @var = a]
----

>
> Ruby has done a lot of checkings, like public/protected/private methods,
> and attr_reader/attr_accessor methods.  For Array, why not just check the
> type/class of obj when the array is created, just like what you do
> for singleton?  If a program has to create and destroy arrays many many
> times, probably it should have been written in C.

On the other hand why not add this type of functionality yourself
----
class Array
    def self.my_new (nums)
         new(nums).collect! {yield}
    end
end

class A; end
p Array.my_new(3){ A.new }
----
[#<A:0xa047048>, #<A:0xa046dc8>, #<A:0xa046d68>]
----

/Christoph