Just found a round problem

ruby-talk
1

irb(main):026:0> 10.499999999999999.round
=> 10
irb(main):027:0> 10.4999999999999999.round
=> 11

Does this happen due to the float problem in any languages including ruby?
Thanks.

2

Thats IEEE 754 float behaviour, yes. python behaves exactly the same.

- --
Florian Gilcher

smtp: flo@andersground.net
jabber: Skade@jabber.ccc.de
gpg: 533148E2

···

On Nov 29, 2009, at 12:06 AM, Ruby Newbee wrote:

irb(main):026:0> 10.499999999999999.round
=> 10
irb(main):027:0> 10.4999999999999999.round
=> 11

Does this happen due to the float problem in any languages including ruby?
Thanks.

3

Florian Gilcher wrote:

irb(main):026:0> 10.499999999999999.round
=> 10
irb(main):027:0> 10.4999999999999999.round
=> 11

Does this happen due to the float problem in any languages including
ruby?
Thanks.

Thats IEEE 754 float behaviour, yes. python behaves exactly the same.

- --
Florian Gilcher

And PHP 5 as well.

php -r 'echo sprintf ("PHP Version = %s\nround(10.499999999999999) =
%d\nround(10.4999999999999999) = %d\n", phpversion(),
round(10.499999999999999), round(10.4999999999999999));'

PHP Version = 5.2.6
round(10.499999999999999) = 10
round(10.4999999999999999) = 11

···

On Nov 29, 2009, at 12:06 AM, Ruby Newbee wrote:

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Posted via http://www.ruby-forum.com/\.

4

Thanks all~

···

2009/11/29 Steve Wilhelm <steve@studio831.com>:

Florian Gilcher wrote:

On Nov 29, 2009, at 12:06 AM, Ruby Newbee wrote:

irb(main):026:0> 10.499999999999999.round
=> 10
irb(main):027:0> 10.4999999999999999.round
=> 11

Does this happen due to the float problem in any languages including
ruby?
Thanks.

Thats IEEE 754 float behaviour, yes. python behaves exactly the same.

And PHP 5 as well.

5

In C i think its 14/15 significant digits and its probably why.

If you want that much precision, find a way to use a bigger float.

···

On Sun, Nov 29, 2009 at 3:34 AM, Ruby Newbee <rubynewbee@gmail.com> wrote:

Thanks all~

2009/11/29 Steve Wilhelm <steve@studio831.com>:
> Florian Gilcher wrote:
>
>> On Nov 29, 2009, at 12:06 AM, Ruby Newbee wrote:
>>
>>> irb(main):026:0> 10.499999999999999.round
>>> => 10
>>> irb(main):027:0> 10.4999999999999999.round
>>> => 11
>>>
>>>
>>> Does this happen due to the float problem in any languages including
>>> ruby?
>>> Thanks.
>>
>>
>> Thats IEEE 754 float behaviour, yes. python behaves exactly the same.
>>

>>
>
> And PHP 5 as well.
>

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Horofox @ irc.freenode.net | #ruby, #ubuntu & #rails
Thiago Fernandes Massa
11 83979414

6

Thiago Massa wrote:

In C i think its 14/15 significant digits and its probably why.

If you want that much precision, find a way to use a bigger float.

BigDecimal and Rational will do the trick.

Best,

···

--
Marnen Laibow-Koser
http://www.marnen.org
marnen@marnen.org
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