Recent changes to 20: double to unsigned long long precision errorhttps://sourceforge.net/p/cppcms/feature-requests/20/2013-02-26T08:44:28.089000ZRecent changes to 20: double to unsigned long long precision error#20 double to unsigned long long precision error2013-02-26T08:44:28.089000Z2013-02-26T08:44:28.089000ZArtyom Beilishttps://sourceforge.net/u/artyom-beilis/https://sourceforge.net97f53539bb387668c991eb76b9cac847fdce3e09<div class="markdown_content"><ul>
<li><strong>milestone</strong>: 1.2 --> 2.0</li>
</ul></div>#20 double to unsigned long long precision error2013-02-26T08:42:47.246000Z2013-02-26T08:42:47.246000ZArtyom Beilishttps://sourceforge.net/u/artyom-beilis/https://sourceforge.net62e5c1ea0478a37f6c685fb09c3506e97f4664f4<div class="markdown_content"><p>Ticket moved from /p/cppcms/bugs/94/</p></div>#94 double to unsigned long long precision error2013-02-26T08:42:25.231000Z2013-02-26T08:42:25.231000ZArtyom Beilishttps://sourceforge.net/u/artyom-beilis/https://sourceforge.netf7ac15ae3d98d7cd3ca62df9c6e9b61b7fea48a4<div class="markdown_content"><ul>
<li><strong>status</strong>: open --> pending</li>
</ul></div>double to unsigned long long precision error2013-02-25T13:15:09.625000Z2013-02-25T13:15:09.625000ZAnonymoushttps://sourceforge.net/u/userid-None/https://sourceforge.netc3194143a0661b814473354728a45b04a7c096e4<div class="markdown_content"><p>Hi, there is a bug with unsigned long long values. At least on my system where sizeof(unsigned long long) = sizeof(double) = 8</p>
<p>The problem is that internally you use double for all intergral types, which might cause<br />
loss of precision for big unsigned long long numbers.</p>
<p>this fails on my system:</p>
<div class="codehilite"><pre><span class="n">unsigned</span> <span class="n">long</span> <span class="n">long</span> <span class="n">ullValue</span> <span class="p">=</span> 63660062001020978<span class="p">;</span>
<span class="n">double</span> <span class="n">doubleValue</span> <span class="p">=</span> 63660062001020978<span class="p">;</span>
<span class="n">double</span> <span class="n">unsignedlonglong_to_double</span> <span class="p">=</span> <span class="n">static_cast</span><span class="o"><</span><span class="n">double</span><span class="o">></span><span class="p">(</span><span class="n">ullValue</span><span class="p">);</span>
<span class="n">unsigned</span> <span class="n">long</span> <span class="n">long</span> <span class="n">double_to_unsignedlonglong</span> <span class="p">=</span> <span class="n">static_cast</span><span class="o"><</span><span class="n">unsigned</span> <span class="n">long</span> <span class="n">long</span><span class="o">></span><span class="p">(</span><span class="n">doubleValue</span><span class="p">);</span>
<span class="n">qDebug</span><span class="p">()</span> <span class="o"><<</span> "<span class="n">unsigned</span> <span class="n">long</span> <span class="n">long</span><span class="p">:</span> " <span class="o"><<</span> <span class="n">ullValue</span><span class="p">;</span>
<span class="n">qDebug</span><span class="p">()</span> <span class="o"><<</span> "<span class="n">double</span><span class="p">:</span> " <span class="o"><<</span> <span class="n">doubleValue</span><span class="p">;</span>
<span class="n">qDebug</span><span class="p">()</span> <span class="o"><<</span> "<span class="n">unsigned</span> <span class="n">long</span> <span class="n">long</span> <span class="n">to</span> <span class="n">double</span><span class="p">:</span> " <span class="o"><<</span> <span class="n">unsignedlonglong_to_double</span><span class="p">;</span>
<span class="n">qDebug</span><span class="p">()</span> <span class="o"><<</span> "<span class="n">double</span> <span class="n">to</span> <span class="n">unsigned</span> <span class="n">long</span> <span class="n">long</span><span class="p">:</span> " <span class="o"><<</span> <span class="n">double_to_unsignedlonglong</span><span class="p">;</span>
</pre></div>
<p>output is:</p>
<p>unsigned long long: 63660062001020978 <-- compare this<br />
double: 6.36601e+16<br />
unsigned long long to double: 6.36601e+16<br />
double to unsigned long long: 63660062001020976 <-- with this</p>
<p>cast from double <--> unsigned long long might cause problems both ways.</p></div>double to unsigned long long precision error2013-02-25T13:15:09.625000Z2013-02-25T13:15:09.625000ZAnonymoushttps://sourceforge.net/u/userid-None/https://sourceforge.net85dbbec2446eb275c9a13990b2c2081e0d2aaa31<div class="markdown_content"><p>Ticket 20 has been modified: double to unsigned long long precision error<br />
Edited By: Artyom Beilis (artyom-beilis)<br />
_milestone updated: u'1.2' => u'2.0'</p></div>double to unsigned long long precision error2013-02-25T13:15:09.625000Z2013-02-25T13:15:09.625000ZAnonymoushttps://sourceforge.net/u/userid-None/https://sourceforge.net92f18c97dcc94457ede06594634dd76e15e3b107<div class="markdown_content"><p>Ticket 94 has been modified: double to unsigned long long precision error<br />
Edited By: Artyom Beilis (artyom-beilis)<br />
Status updated: u'open' => u'pending'</p></div>