From: Dmitrii Samoilov <redmine@...>
Date: 2010-12-08T21:02:56+09:00
Subject: [ruby-core:33637] [Ruby 1.9-Bug#4135][Open] bug in calculations in 1.9.3dev / 1.9.2

Bug #4135: bug in calculations in 1.9.3dev / 1.9.2
http://redmine.ruby-lang.org/issues/show/4135

Author: Dmitrii Samoilov
Status: Open, Priority: High
Category: core, Target version: 1.9.x
ruby -v: ruby 1.9.3dev (2010-12-08 trunk 30125) [i686-linux]

$ 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


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