How to sum if we use substring function - xslt

Question

I want to ask how to get total amount if we use substring function,
for example I have this xml,
<document>
<line id="0">
<field id="0"><![CDATA[AAAddd17aaass]]></field>
</line>
<line id="1">
<field id="0"><![CDATA[DDDaaa33sssaa]]></field>
</line>
</document>
I should sum(substring(field[#id='0'], 7,2)). Then I try to do that, I get this error message: Current Item is 'NaN of type xs:string. (I try to use number function but it doesn't help)
Please advice me how to solve it.

Answer 1

Easy in XSLT 2.0:
sum(field[#id='0']/number(substring(., 7,2)))
Rather more difficult in XSLT 1.0: see for example http://www.velocityreviews.com/forums/t170401-sum-over-computed-value.html

Answer 2

In XSLT 1.0 if you don't want to write recursive templates yourself, you can use the transform-and-sum template from FXSL.
See how to use it here.
Here is the full transformation:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:f="http://fxsl.sf.net/"
xmlns:func-transform="f:func-transform"
exclude-result-prefixes="xsl f func-transform"
>
<xsl:import href="transform-and-sum.xsl"/>
<!-- to be applied on testTransform-and-sum.xml -->
<xsl:output method="text"/>
<func-transform:func-transform/>
<xsl:template match="/">
<xsl:call-template name="transform-and-sum">
<xsl:with-param name="pFuncTransform"
select="document('')/*/func-transform:*[1]"/>
<xsl:with-param name="pList" select="/*/*/*"/>
</xsl:call-template>
</xsl:template>
<xsl:template match="func-transform:*" mode="f:FXSL">
<xsl:param name="arg1" select="0"/>
<xsl:value-of select="number(substring($arg1, 7,2))"/>
</xsl:template>
</xsl:stylesheet>
when applied on the provided XML document:
<document>
<line id="0">
<field id="0"><![CDATA[AAAddd17aaass]]></field>
</line>
<line id="1">
<field id="0"><![CDATA[DDDaaa33sssaa]]></field>
</line>
</document>
the wanted, correct result is produced:
50