Bug #4135: bug in calculations in 1.9.3dev / 1.9.2

• Status: Rejected
• Assignee: -
• Target version: 2.0.0
• ruby -v: ruby 1.9.3dev (2010-12-08 trunk 30125) [i686-linux]

[german (Dmitrii Samoilov)]

=begin
$ ruby -v
ruby 1.9.3dev (2010-12-08 trunk 30125) [i686-linux]

I just installed ruby-head from rvm and run this in irb:

$ irb
ruby-head > 125.33 - (125.33/100.0*50.0)
=> 62.66499999999999
ruby-head > 125.33 / 100.0 * 50.0
=> 62.665000000000006
ruby-head > 15.33 / 100.0 * 50.0
=> 7.664999999999999
ruby-head > (15.33 / 100.0) * 50.0
=> 7.664999999999999
ruby-head > (14.33 / 100.0) * 50.0
=> 7.165000000000001

Which is obviously wrong.

The same in old ruby 1.9.2.dev

$ ruby -v
ruby 1.9.2dev (2009-07-18 trunk 24186) [i686-linux]
$ irb
ruby-1.9.2-preview1 > (14.33 / 100.0) * 50.0
=> 7.165000000000001

Ruby 1.8.7 looks good
$ ruby -v
ruby 1.8.7 (2010-04-19 patchlevel 253) [i686-linux], MBARI 0x8770, Ruby Enterprise Edition 2010.02

$ irb
irb(main):001:0> (14.33 / 100.0) * 50.0
=> 7.165
=end

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Rejected

=begin

=end

[naruse (Yui NARUSE)]

=begin
Learn floating point numbers.

What Every Computer Scientist Should Know About Floating-Point Arithmetic
http://docs.sun.com/source/806-3568/ncg_goldberg.html
http://wiki.github.com/rdp/ruby_tutorials_core/ruby-talk-faq#floats_imprecise
http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems
=end

[german (Dmitrii Samoilov)]

=begin
Stupid me. Sorry guys.
=end