RE: [xsl] Unexpected result in sum

Subject: RE: [xsl] Unexpected result in sum
From: "Angela Williams" <Angela.Williams@xxxxxxxxxxxxxxxxxx>
Date: Fri, 9 Nov 2007 15:15:07 -0600
Thank you for the reply, Abel.

No, I don't expect the minus sign; I expect an unsigned or positive 0.

When I declare the type as xs:double+, I still get the unexpected value.

Curiously, if I add the leading / in the select, the value 0 *is*
<xsl:variable name="nodes" select="/b"/>

Also, if I change the variable to the following, I get 0 (no sign) but
this feels like an in-efficient hack:

<xsl:variable name="nodes" as="xs:decimal+">
   <xsl:for-each select="$nodes">
      <xsl:value-of select="number( . )"/>

Is there a more efficient way of accomplishing this?


-----Original Message-----
From: Abel Braaksma []
Sent: Friday, November 09, 2007 2:14 PM
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: [xsl] Unexpected result in sum

I'm not 100% sure I really understand your question (do you expect the
minus sign or don't you?) but I think any problem like this lies in the
fact that when you use sum() on undeclared values, you sum them as
xs:double, which is an unprecise floating point type, resulting in the
sum being close to zero, but not exactly zero. I haven't tried your code
yet, but if you declare your $nodes variable as xs:decimal+ I think you
will get the expected result:

<xsl:variable name="nodes" select="b" as="xs:decimal+"/>

When doing numerics, I always force myself to use typed variables. You
can use any simple type with a Basic processor, and xs:decimal is a
simple type.

Come to think of it, when you force yourself to *always* use typed
variables, you will win on three ends: your code will be more readable,
the processor will have more hints to optimize for speed and, most
importantly, coding problems (bugs) will be found way easier because the
compiler has more to tell you on each error.

Hope this points you in the right direction,

-- Abel Braaksma

Angela Williams wrote:
> Why does this not output 0.00?  When formatted, I end up with -$0.00.
> I've read what I can find on negative zero, but can't see how this
> node set and operation could produce it.
> Using Saxon 8.9 processor (internal to Oxygen.)
> Input:
> <?xml version="1.0" encoding="UTF-8"?> <a>
>     <b>1103.86</b>
>     <b>1829.30</b>
>     <b>-853.77</b>
>     <b>-243.17</b>
>     <b>-1.11</b>
>     <b>-1296.66</b>
>     <b>588.52</b>
>     <b>849.25</b>
>     <b>-1976.22</b>
> </a>
> Output:
> <?xml version="1.0" encoding="UTF-8"?> <a>
>    <sum-b>-2.2737367544323206E-13</sum-b>
>    <sum-nodes>-2.2737367544323206E-13</sum-nodes>
> </a>
> <xsl:stylesheet xmlns:xsl="";
> version="2.0">
>     <xsl:output method="xml" indent="yes"/>
>     <xsl:template match="/a">
>         <a>
>             <sum-b>
>                 <xsl:value-of select="sum(b)"/>
>             </sum-b>
>             <xsl:variable name="nodes" select="b"/>
>             <sum-nodes>
>                 <xsl:value-of select="sum($nodes)"/>
>             </sum-nodes>
>         </a>
>     </xsl:template>
> </xsl:stylesheet>
> Thanks!
> Angela Williams
> Office: 512.344.1547 ~ Fax: 512.397.6656
> Angela.Williams@xxxxxxxxxxxxxxxxxx

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