From: "Shot (Piotr Szotkowski)" <shot@...>
Date: 2009-12-22T01:34:01+09:00
Subject: Re: Ruby's implementation of Fixnum-assignment

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RichardOnRails:

> 1. Integer's in the range -2**30 to 2**30-1 are
> Fixnum's. Integers outside that range are Bignum's

Depending on the architecture:

>> (2**62-1).class
=3D> Fixnum
>> (2**62).class
=3D> Bignum
>> RUBY_DESCRIPTION
=3D> "ruby 1.9.1p376 (2009-12-07 revision 26041) [x86_64-linux]"

> 2. For Fixnum "i", i's object_id is twice i's value plus 1. Said
> another way, i's object_id is i's binary value left-shifted with
> 1 as padding.

Right, Fixnums are immediate in Ruby (at least in MRI).

> 3. Object_id's of Bignum's close to the boundaries of Fixnum's
> bear no apparent relationship to the Fixnum object_id's.

Right, because Bignums are =E2=80=98regular=E2=80=99 objects.

> For Fixnums, the object_id IS the value, just a little shifted.

Spot on.

There was a very nice talk about these things; you might want to google
for "Understanding Ruby's Object Model" (the top links do not open for
me at the moment, so I=E2=80=99m not sure this is the talk I think of).

=E2=80=94 Shot
--=20
Clinical psychology seems designed for people too
smart for religion but not smart enough for science.
                   [Paul Lutus, Asperger=E2=80=99s by Proxy]

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