From: Mark Hubbart <discordantus@...>
Date: 2005-05-05T02:06:07+09:00
Subject: Re: Fixnum's binary representation

On 5/4/05, camsight@gmail.com <camsight@gmail.com> wrote:
> Thanks, Robert!
> 
> > For which numbers do you have problems?  I don't see any so far
> 
> I mean...
> If Bignum#[] is made to simulate 32-bit signed integers, it can't show
> numbers with more than 32-bit representation.
> Well, positive numbers will be okay.
> But what about negative numbers?
> When can I expect the sign bit?
> I assume that numbers beyond 32-bit are not suitable for Bignum#[].
> Do you agree?

IIUC, it's not precisely a "sign bit"; it's more like an entire
bit-flip. -1 is zero, bit-flipped. So if you are trying to use
Integer#[] to get determine the sign of a number, the question is
simply: how high do you want to go? integer[512] will correctly
determine sign for numbers in the range of (-(2**512-1)..2**512) (that
is, a 512 bit integer). There no way (that I can think of) to use
Integer#[] to return the correct sign on *any* integer usable in Ruby.

hth,
Mark