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XML:

<?xml version="1.0"?>
<page>
  <year>2002</year>
  <month num="3" start="6" days="31">March, 2002</month>
  <day>19</day>
</page>

XSL:

<?xml version="1.0"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:variable name="start" select="/page/month/@start"/>
<xsl:variable name="count" select="/page/month/@days"/>
<xsl:variable name="total" select="$start + $count - 1"/>
<xsl:variable name="overflow" select="$total mod 7"/>
<xsl:variable name="nelements">
<xsl:choose>
<xsl:when test="$overflow > 0"><xsl:value-of select="$total + 7 - $overflow"/></xsl:when>
<xsl:otherwise><xsl:value-of select="$total"/></xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:template match="/">
<table border="1" bordercolor="#88A5DB" width="100%">
<tr align="center">
<td> </td>
<td><b><xsl:value-of select="/page/month"/></b></td>
<td> </td>
</tr>
</table><br/>
<table border="1" bordercolor="#88A5DB" width="100%">
<tr align="center">
<td width="150">Sunday</td>
<td width="150">Monday</td>
<td width="150">Tuesday</td>
<td width="150">Wendsday</td>
<td width="150">Thirsday</td>
<td width="150">Friday</td>
<td width="150">Saturday</td>
</tr>
<xsl:call-template name="month"/>
</table>
</xsl:template>
<!-- Called only once for root -->
<!-- Uses recursion with index + 7 for each week -->
<xsl:template name="month">
<xsl:param name="index" select="1"/>
<xsl:if test="$index < $nelements">
<xsl:call-template name="week">
<xsl:with-param name="index" select="$index"/>
</xsl:call-template>
<xsl:call-template name="month">
<xsl:with-param name="index" select="$index + 7"/>
</xsl:call-template>
</xsl:if>
</xsl:template>
<!-- Called repeatedly by month for each week -->
<xsl:template name="week">
<xsl:param name="index" select="1"/>
<tr height="50" valign="top">
<xsl:call-template name="days">
<xsl:with-param name="index" select="$index"/>
<xsl:with-param name="counter" select="$index + 6"/>
</xsl:call-template>
</tr>
</xsl:template>
<!-- Called by week -->
<!-- Uses recursion with index + 1 for each day-of-week -->
<xsl:template name="days">
<xsl:param name="index" select="1"/>
<xsl:param name="counter" select="1"/>
<xsl:choose>
<xsl:when test="$index < $start">
<td bgcolor="#eeeeee">-</td>
</xsl:when>
<xsl:when test="$index - $start + 1 > $count">
<td bgcolor="#eeeeee">-</td>
</xsl:when>
<xsl:when test="$index > $start - 1">
<td>
<xsl:if test="/page/day[.=($index - $start + 1)]">
<xsl:attribute name="bgcolor">#ffeeee</xsl:attribute>
</xsl:if>
<xsl:value-of select="$index - $start + 1"/>
<xsl:if test="/page/day[.>=($index - $start + 1)]">
<p align="right"><br/></p>
</xsl:if>
</td>
</xsl:when>
</xsl:choose>
<xsl:if test="$counter > $index">
<xsl:call-template name="days">
<xsl:with-param name="index" select="$index + 1"/>
<xsl:with-param name="counter" select="$counter"/>
</xsl:call-template>
</xsl:if>
</xsl:template>
</xsl:stylesheet>

这段 XSL 常常让我想起当年啃 prolog 的情形。当时花了很多时间才搞清楚用递归来实现循环。

XSL 也可以用递归来实现循环。