From: Rob Biedenharn <Rob@...>
Date: 2007-09-25T09:33:26+09:00
Subject: Re: object_id 1, 2, 3

$ irb
irb(main):001:0> true.object_id
=> 2
irb(main):002:0> nil.object_id
=> 4
irb(main):003:0> false.object_id
=> 0

I saw a flowchart somewhere (online?) that showed how the least- 
significant bits were used by the interpreter in the implementation  
of some "objects" which were both common and immutable (TrueClass,  
FalseClass, NilClass, Fixnum).

The LSB=1 is Fixnum (hence the object_id of n would be (n<<1)|0x01 in  
the underlying C code).

-Rob

On Sep 24, 2007, at 8:14 PM, SpringFlowers AutumnMoon wrote:

> Fixnum   object_id
> 0            1
> 1            3
> 2            5
>
> -1          -1
> -2          -3
>
>
> so the question is...  which objects have the object_id 2, 4, 6,  
> and -2,
> -4, etc?
>
>
>
>
> irb(main):041:0> a = 0
> => 0
> irb(main):042:0> a.object_id
> => 1
>
> irb(main):043:0> a = 1
> => 1
> irb(main):044:0> a.object_id
> => 3
>
> irb(main):045:0> a = 2
> => 2
> irb(main):046:0> a.object_id
> => 5
>
> irb(main):047:0> a = -1
> => -1
> irb(main):048:0> a.object_id
> => -1
>
> irb(main):049:0> a = -2
> => -2
> irb(main):050:0> a.object_id
> => -3
> -- 

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com