Just found a round problem

Ruby
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

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Nov 29, 2009, at 12:06 AM, Ruby N. 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 G.

smtp: [email protected]
jabber: [email protected]
gpg: 533148E2

-----BEGIN PGP SIGNATURE-----
Version: GnuPG/MacGPG2 v2.0.12 (Darwin)

iEYEARECAAYFAksR80wACgkQyLKU2FMxSOLkpwCdFwIj6FfsGK3+ZFFVLPQV0XwJ
Xa8AnAp6o5sxct7fsDrJUWUkIJ0QmB19
=bERM
-----END PGP SIGNATURE-----

3

Florian G. wrote:

On Nov 29, 2009, at 12:06 AM, Ruby N. 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 G.

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

4

Thanks all~

2009/11/29 Steve W. [email protected]:

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.

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.

6

Thiago M. 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
[email protected]