Perhaps the algorithm is clearer when rewritten in XSLT 2.0:
<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
version="1.0">
<xsl:function name="f:total-sales-value" as="xs:decimal">
<xsl:param name="list" as="xs:decimal*"/>
<xsl:choose>
<xsl:when test="exists($list)">
<xsl:sequence select="$list[1]/(sales*price) +
f:total-sales-value($list[position()!=1])"/>
</xsl:when>
<xsl:otherwise>
<xsl:sequence select="0"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template match="/">
Total sales value is: <xsl:value-of
select="format-number(f:total-sales-value(//book)), '$#.00')"/>
</xsl:template>
</xsl:stylesheet>
But of course in 2.0 you don't need recursion, you can write
sum(//book/(sales*price))
Michael Kay
http://www.saxonica.com/
-----Original Message-----
From: hanged(_dot_)man(_at_)lycos(_dot_)com
[mailto:hanged(_dot_)man(_at_)lycos(_dot_)com]
Sent: 05 September 2006 16:53
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [xsl] Two versions of sum over node list by
recursion--why and how does second one work?
Here are two examples of summing a node list by recursion:
the first sends the result of the addition back to itself by
a parameter: the second does not. The first was posted by G.
Ken Holman--the second is from Michael Kay s _XSLT
Programmer's Reference_.
I know that Mr. Kay's code works...I just can't figure out _why_.
FIRST EXAMPLE:
<xsl:template match="/">
<xsl:variable name="result-text">
<xsl:text/>0<xsl:apply-templates select="/*/RECEIPT[1]"
mode="equation"/>
</xsl:variable>
<xsl:variable name="result" select="number($result-text)"/>
<xsl:value-of select="$result"/>
</xsl:template>
<xsl:template match="RECEIPT" mode="equation">
<xsl:param name="result" select="0"/>
<xsl:variable name="this" select="$result + ( qtyRcpt * line/pr )"/>
<xsl:choose>
<xsl:when test="following-sibling::RECEIPT">
<xsl:apply-templates select="following-sibling::RECEIPT[1]"
mode="equation">
<xsl:with-param name="result" select="$this"/>
</xsl:apply-templates>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$this"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
SECOND EXAMPLE:
<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
version="1.0">
<xsl:template name="total-sales-value">
<xsl:param name="list"/>
<xsl:choose>
<xsl:when test="$list">
<xsl:variable name="first" select="$list[1]"/>
<xsl:variable name="total-of-rest">
<xsl:call-template name="total-sales-value">
<xsl:with-param name="list"
select="$list[position()!=1]"/>
</xsl:call-template>
</xsl:variable>
<xsl:value-of select="$first/sales * $first/price +
$total-of-rest"/>
</xsl:when>
<xsl:otherwise>0</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template match="/">
<xsl:variable name="total">
<xsl:call-template name="total-sales-value">
<xsl:with-param name="list" select="//book"/>
</xsl:call-template>
</xsl:variable>
Total sales value is: <xsl:value-of select="format-number($total,
'$#.00')"/>
</xsl:template>
</xsl:stylesheet>
QUESTION:
In Mr. Kay's example, why does the variable $total-of-rest
indeed contain the total and not just the result of the
addition in the last recursion?
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