OpenEuphoria

Re: Big Integer Atoms

• Posted by "Igor Kachan" <kinz at peterlink.ru> Jul 12, 2004
• 580 views

Robert Craig wrote:
-----
> From: Robert Craig <guest at RapidEuphoria.com>
> To: EUforum at topica.com
> Subject: Re: Big Integer Atoms
> Sent: 12 jul 2004 y. 1:31
> 
> posted by: Robert Craig <rds at RapidEuphoria.com>
> 
> Igor Kachan wrote:
> > 
> > Hi, dear Euphorians,
> > 
> > The EU manual says:
> > 
> > "... Those declared with type integer must be atoms 
> > with integer values from -1073741824 to +1073741823
> > inclusive. 
> > You can perform exact calculations on larger integer
> > values, up to about 15 decimal digits, but declare 
> > them as atom, rather than integer ..."
> > 
> > This "up to about 15 decimal digits" seems to be not
> > enough concrete thing for some cases.
> > 
> > Couldn't someone tell me about more precise
> > bounds of these "larger integer values"?
> 
> (As I recall) with IEEE floating-point, you have 1 bit 
> for the +/- sign, 52 bits for the mantissa, and 11 bits 
> for the exponent.
>  
> When storing integers in f.p. form, 
> at some point you are going to use up all 52 bits in 
> the mantissa, and you won't be able to store the integers
> exactly anymore, or get exact results from your > calculations.
> I guess you could look for the point where:
>    x + 1 = x
> i.e. you don't have the resolution to distinguish between
> one huge integer and the next. There's roughly 3 decimal
> digits per 10 binary digits, so I guess that would be
> around 52 * 3 / 10 = 15 decimal digits, roughly.

Thanks, I'll try to get the experimental
bounds by this method, useing printf(), floor() etc.

Regards,
Igor Kachan
kinz at peterlink.ru