Re: Doing math in XSLT?

I have the following XML

<row>
B B B B <entry nameend="col2" namest="col1">
B B B B B B B  <p>OpenID Connect client settings</p>
B B B B B B B  <note
B B B B B B B B B B B  id="note_N1055C"
B B B B B B B B B B B  >The following parameters are only applicable
B B B B B B B B B B B  when this client supports the OpenID Connect use
B B B B B B B B B B B  cases.</note>
B B B B </entry>
</row>

The attributes nameend="col2" namest="col1" indicate that this row
spans 2 columns (end - start + 1).

I've tried this to try and get the numbers 1 and 2 from these strings,
but I get NaN errors

<xsl:variable name="start"
B B B B select="number(substring-after(@namest, 'col'))" as="xs:double"/>
<xsl:variable name="end"
B B B B select="number(substring-after(@nameend, 'col'))" as="xs:double"/>

I've tried this in different combinations with/without the
as="xs:double" and number() and those variations throw the same error.

B  <xsl:template match="entry">
<xsl:variable name="start"
B B B  select="number(substring-after(@namest, 'col'))" as="xs:double"/>
<xsl:variable name="end"
B B B  select="number(substring-after(@nameend, 'col'))" as="xs:double"/>
B B B  <xsl:comment>{$end - $start + 1}</xsl:comment>
B  </xsl:template>

doesn't give any error with Saxon HE 12 and outputs e.g. <!--2--> for
your sample XML.

Please show us minimal but complete code that gives that error and tell
us which XSLT processor and version you use.