Strange behavior in Integer

Ruby
1

new user on MacOsX.
Ruby version: ruby 1.8.2 (2004-12-25) [universal-darwin8.0]
intel MacBook Pro

Working thru the examples in Programming Ruby, I got what I didn’t
expect:

Integer(33.80 * 100) ==> 3379

however,

Integer(3.380 * 1000) ==> 3380

Doesn’t seem like a floating point round off error.

joe

2

Joe Davison wrote:

Integer(33.80 * 100) ==> 3379

however,

Integer(3.380 * 1000) ==> 3380

Doesn’t seem like a floating point round off error.

“%.30f” % (33.80 * 100)
=> “3379.999999999999545252649113535881”

Seems like one to me.

HTH,
Sebastian

3

On Mon, Aug 4, 2008 at 5:02 PM, Sebastian H.
[email protected] wrote:

=> “3379.999999999999545252649113535881”

Seems like one to me.

HTH,
Sebastian

Just playing around a little (no exhaustive testing), but it seems
like this only happens with a number string matching
/\A3[2-9].[38]0*\Z/ (for nubies, a number that is in the closed
interval 32 to 40 with a following 3 or 8 in the decimal place and
nothing after it except for zero or more zeros). Weird. There might
be other cases.

I’m using the 1.8.7 ruby ver, btw.

Todd

4

Todd B. [email protected] writes:

Just playing around a little (no exhaustive testing), but it seems
like this only happens with a number string matching
/\A3[2-9].[38]0*\Z/ (for nubies, a number that is in the closed
interval 32 to 40 with a following 3 or 8 in the decimal place and
nothing after it except for zero or more zeros). Weird. There might
be other cases.

http://docs.sun.com/source/806-3568/ncg_goldberg.html

5

On Mon, Aug 4, 2008 at 7:58 PM, Joost D. [email protected]
wrote:

Todd B. [email protected] writes: There might

be other cases.

http://docs.sun.com/source/806-3568/ncg_goldberg.html

Indeed. These errors occur starting with 32, then 512, then 8192,
etc. with expanding ranges. The pattern I get, but I don’t
understand, though, why 3 and 8?

Todd