From: Seebs <usenet-nospam@...>
Date: 2009-09-14T14:25:07+09:00
Subject: Re: Overflow behavior

On 2009-09-13, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
> jacob navia wrote:
>> What is the official behavior of ruby in case of integer overflow?
>
> Integers overflow from Fixnums (30 bits) into Bignums (unlimited 
> precision integers).
>
> irb(main):003:0> x = 2**30 - 1
>=> 1073741823
> irb(main):004:0> x.class
>=> Fixnum
> irb(main):005:0> x+1
>=> 1073741824
> irb(main):006:0> (x+1).class
>=> Bignum

I looked briefly at the code underlying this.  I am not totally convinced that
it's impossible for a calculation (especially a multiplication) to evade the
overflow detection used.

-s
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