Prev: optparser question
Next: Newbie
From: Neve Le on 30 Jun 2010 08:06
Siep Korteling wrote:
>> Xavier Noria wrote:
>> That 15 is hard-coded in the definition of Float#to_s.
>
> Yes, and exposing more digits is not accurate:
> The float is bogus after the 16th digit.


Working with big numbers here, it seems that precision is only
guaranteed to 15 digits on either side of the decimal. When a whole
number >15 digits is divided the decimal is approximated, and anything
>17 digits prints a float of n.0 no matter how it's "%n.nf" formatted.


Is the hard-coded 15 just a "safe" limit? Would I be able to recompile
ruby with a higher definition? If possible, how high could I go?
--
Posted via http://www.ruby-forum.com/.

From: Brian Candler on 30 Jun 2010 08:32
Neve Le wrote:
> Is the hard-coded 15 just a "safe" limit? Would I be able to recompile
> ruby with a higher definition? If possible, how high could I go?

No, it's a limit of IEEE double-precision floating-point representation.

If you want more digits of precision, use BigDecimal.
--
Posted via http://www.ruby-forum.com/.

From: Giampiero Zanchi on 30 Jun 2010 08:44

http://www.ruby-forum.com/topic/208840#new

hope this help
--
Posted via http://www.ruby-forum.com/.

From: brabuhr on 30 Jun 2010 08:48
On Wed, Jun 30, 2010 at 8:06 AM, Neve Le <nevele(a)gmx.com> wrote:
> Siep Korteling wrote:
>>> Xavier Noria wrote:
>>> That 15 is hard-coded in the definition of Float#to_s.
>>
>> Yes, and exposing more digits is not accurate:
>> The float is bogus  after the 16th digit.
>
> Working with big numbers here, it seems that precision is only
> guaranteed to 15 digits on either side of the decimal. When a whole
> number >15 digits is divided the decimal is approximated, and anything
>>17 digits prints a float of n.0 no matter how it's "%n.nf" formatted.

http://ruby-doc.org/core/classes/Float.html
"Float objects represent real numbers using the native architecture‘s
double-precision floating point representation."

http://en.wikipedia.org/wiki/Double_precision_floating-point_format

You could try BigDecimal.

From: Javier Goizueta on 30 Jun 2010 10:56
You may also want to take a look at http://flt.rubyforge.org/

It's an implementation of arbitrary precision floating point numbers
(decimal and binary). If you don't need it to be fast it has some
advantages over BigDecimal.
--
Posted via http://www.ruby-forum.com/.

 | 
Pages: 1
Prev: optparser question
Next: Newbie