[xsl] Calculating cumulative values and min/max

["Simon Shutter" <simon@xxxxxxxxxxx>]

A few months ago I asked for some help with aggregating numbers in XSLT 1.0.
Andrew Welch provided the stylesheet below that worked just fine for my
needs.

I have a couple of follow-up questions:

a) in the predicate [@x = current()/@x], why is current node used and not
the context node used?  I guess I'm confused at to which @x is which in the
predicate.

b) is it possible to calculate min/max values is this only possible in
XSLT/XPATH 2.0?

Thanks, Simon


---------------------------------------------
Stylesheet
---------------------------------------------
<xsl:template match="point">
 <xsl:copy>
   <xsl:copy-of select="@*"/>
   <xsl:attribute name="y2">
     <xsl:value-of select="sum(./@y1|preceding-sibling::point[@x =
current()/@x]/@y1)"/>
   </xsl:attribute>
 </xsl:copy>
</xsl:template>

---------------------------------------------
Input
---------------------------------------------

<root id="theroot">
  <set id="1">
    <point x="1" y1="2" />
    <point x="1" y1="3" />
    <point x="1" y1="0" />
    <point x="1" y1="2" />
    <point x="1" y1="2" />
    <point x="2" y1="3" />
    <point x="2" y1="0" />
    <point x="2" y1="2" />
    <point x="3" y1="2" />
    <point x="3" y1="3" />
    <point x="3" y1="1" />
    <point x="3" y1="2" />
    <point x="3" y1="2" />
  </set>
  <set id="2">
    <point x="1" y1="2" />
    <point x="1" y1="3" />
    <point x="1" y1="0" />
    <point x="1" y1="2" />
    <point x="2" y1="2" />
    <point x="3" y1="2" />
    <point x="3" y1="2" />
    <point x="3" y1="2" />
  </set>
  <set id="n">
    <point x="1" y1="2" />
    <point x="1" y1="3" />
    <point x="1" y1="2" />
    <point x="2" y1="3" />
    <point x="2" y1="0" />
    <point x="2" y1="2" />
    <point x="3" y1="3" />
  </set>
</root>