From: Magnus Holm <judofyr@...>
Date: 2010-11-04T02:11:57+09:00
Subject: [ruby-core:33043] Re: [Ruby 1.9-Bug#4022][Open] Mistake in this cocient of logs followed by %1

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That's just how floats work:

>> Math.log(4913)/Math.log(17) == 3.0
=> false
>> "%.50f" % (Math.log(4913)/Math.log(17))
=> "2.99999999999999955591079014993738383054733276367188"
>> "%.50f" % 3.0
=> "3.00000000000000000000000000000000000000000000000000"

// Magnus Holm


On Wed, Nov 3, 2010 at 17:52, Daniel Silberschmidt <redmine@ruby-lang.org>wrote:

> Bug #4022: Mistake in this cocient of logs followed by %1
> http://redmine.ruby-lang.org/issues/show/4022
>
> Author: Daniel Silberschmidt
> Status: Open, Priority: Normal
> Target version: 1.9.1
> ruby -v: 1.9.1
>
> I get a wrong answer when I apply the following expression:
> Math.log(4913)/Math.log(17) % 1
> This happens in ruby 1.9.1 and in ruby 1.8.7
> With other set of numbers the answers are correct
>
> irb(main):001:0> Math.log(4913)/Math.log(17) % 1
> => 1.0
> irb(main):002:0> Math.log(4913)/Math.log(17)
> => 3.0
> irb(main):003:0> 3.0 % 1
> => 0.0
> irb(main):004:0> (Math.log(4913)/Math.log(17)) % 1
> => 1.0
>
>
> ----------------------------------------
> http://redmine.ruby-lang.org
>
>

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That&#39;s just how floats work:<div><br></div><div><div>&gt;&gt; Math.log(=
4913)/Math.log(17) =3D=3D 3.0</div><div>=3D&gt; false</div><div>&gt;&gt; &q=
uot;%.50f&quot; % (Math.log(4913)/Math.log(17))</div><div>=3D&gt; &quot;2.9=
9999999999999955591079014993738383054733276367188&quot;</div>

<div>&gt;&gt; &quot;%.50f&quot; % 3.0</div><div>=3D&gt; &quot;3.00000000000=
000000000000000000000000000000000000000&quot;</div><div><br></div>// Magnus=
 Holm<br>
<br><br><div class=3D"gmail_quote">On Wed, Nov 3, 2010 at 17:52, Daniel Sil=
berschmidt <span dir=3D"ltr">&lt;<a href=3D"mailto:redmine@ruby-lang.org">r=
edmine@ruby-lang.org</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_qu=
ote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex=
;">

Bug #4022: Mistake in this cocient of logs followed by %1<br>
<a href=3D"http://redmine.ruby-lang.org/issues/show/4022" target=3D"_blank"=
>http://redmine.ruby-lang.org/issues/show/4022</a><br>
<br>
Author: Daniel Silberschmidt<br>
Status: Open, Priority: Normal<br>
Target version: 1.9.1<br>
ruby -v: 1.9.1<br>
<br>
I get a wrong answer when I apply the following expression: Math.log(4913)/=
Math.log(17) % 1<br>
This happens in ruby 1.9.1 and in ruby 1.8.7<br>
With other set of numbers the answers are correct<br>
<br>
irb(main):001:0&gt; Math.log(4913)/Math.log(17) % 1<br>
=3D&gt; 1.0<br>
irb(main):002:0&gt; Math.log(4913)/Math.log(17)<br>
=3D&gt; 3.0<br>
irb(main):003:0&gt; 3.0 % 1<br>
=3D&gt; 0.0<br>
irb(main):004:0&gt; (Math.log(4913)/Math.log(17)) % 1<br>
=3D&gt; 1.0<br>
<br>
<br>
----------------------------------------<br>
<a href=3D"http://redmine.ruby-lang.org" target=3D"_blank">http://redmine.r=
uby-lang.org</a><br>
<br>
</blockquote></div><br></div>

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