title: Sum diff problem/bug in XSLT 1.0
body: <p>I have this XML data and try and make a sum of it using the XSLT snippet below.  </p>
  
  <p><strong>Xml</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;values&gt;
      &lt;value&gt;159.14&lt;/value&gt;
      &lt;value&gt;-2572.50&lt;/value&gt;
      &lt;value&gt;-2572.50&lt;/value&gt;
      &lt;value&gt;2572.50&lt;/value&gt;
      &lt;value&gt;2572.50&lt;/value&gt;
      &lt;value&gt;-159.14&lt;/value&gt;
  &lt;/values&gt;
  </code></pre>
  
  <p><strong>Xslt</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  
  &lt;xsl:stylesheet version="1.0"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform"&gt;
  
  &lt;xsl:template match="/"&gt;
      &lt;xsl:value-of select="sum(values/value)"/&gt;
  &lt;/xsl:template&gt;
  
  &lt;/xsl:stylesheet&gt;
  </code></pre>
  
  <p>In my world the value should then be <strong>0</strong> but it ends up being <strong>-0.0000000000005684341886080801</strong></p>
  
  <p>Run it in Visual Studio and see for yourself. <strong><em>Why?</em></strong> is this happening?</p>