From: Eric Hodel <drbrain@...7.net>
Date: 2008-12-23T13:11:49+09:00
Subject: [ruby-core:20814] Re: [Bug #922] Float == is false when should be true

On Dec 22, 2008, at 19:55 PM, Amanda Nicholas wrote:

> Bug #922: Float == is false when should be true
> http://redmine.ruby-lang.org/issues/show/922
>
> Author: Amanda Nicholas
> Status: Open, Priority: Normal
> Target version: Ruby 1.8.7
>
> In irb on Ruby 1.8.6 (ruby 1.8.6 (2007-09-24 patchlevel 111) [i486- 
> linux]) and 1.8.7 (ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux])
>
>>> 896.5 * 0.83
> => 744.095
>>> 896.5 * 0.83 == 744.095
> => false

They're not the same, Ruby truncates the true value for display  
purposes:

irb(main):001:0> a = 896.5* 0.83
=> 744.095
irb(main):002:0> b = 744.095
=> 744.095
irb(main):004:0> "%0.26f %0.26f" % [a, b]
=> "744.09499999999991359800333157 744.09500000000002728484105319"

See also: http://en.wikipedia.org/wiki/Floating_point