From: Robert Klemme <bob.news@...>
Date: 2005-05-05T01:09:48+09:00
Subject: Re: Fixnum's binary representation

camsight@gmail.com wrote:
> Hi, people!
> 
> As far as I know, Ruby's Fixnum is 30-bit signed integer.
> One bit is used as a flag for whether it's a direct value.
> Another bit is used for non-Fixnum direct values.
> I wondered how Fixnum#[] works and tested it.

> look like.
> My guess is that Fixnum#[] works as if it's 32-bit signed integer.
> It's not showing its real binary representation.
> Is my guess true?

Yes.

> My another question is that even if (2 ** 31 - 1) is not a Fixnum, the
> above code works for it (Actually Bignum#[]).
> If the number is bigger than that, [] doesn't work.

For which numbers do you have problems?  I don't see any so far

>> 100.times {|sh| raise unless sh==0||(1 << sh)[0] == 0}
=> 100
>> (1<<100).class
=> Bignum

> Fixnum#[] and Bignum#[] are cleverly hiding the internal facts and are
> made to simulate 32-bit signed integers?

Yes.

Kind regards

    robert