Your template parseRows is intrinsically tail-recursive - basically this
means that after calling itself, it does nothing else before returning.
It's a rather strange stylesheet because as well as using recursion to
tokenize the string, it also calls xalan:tokenize() - I can't see why!
Saxon and jd.xslt are known to use tail recursion.
To test whether your engine uses tail recursion (on a particular
stylesheet), generate some test data that will cause about 2000 nested
recursive calls. Most processors without tail recursion will fail at
around 500.
Michael Kay
-----Original Message-----
From: owner-xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
[mailto:owner-xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com] On Behalf Of
I-Lin Kuo
Sent: 28 August 2003 14:44
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [xsl] tail-recursion
I have to do some string manipulation. The following takes a
string such as
"1~2~a~!~f~4~5~!~1~2~3" and parses it as a list delimited by
"~!~" and then
processes each list element "1~2~a", "f~4~5", and "1~2~3" as a list
delimited by "~" in order to display as an html table
<xsl:template name="parseRows">
<xsl:param name="catContents"/>
<xsl:param name="font-size" select="'-1'"/>
<xsl:choose>
<xsl:when test="contains($catContents,'~!~')">
<xsl:call-template name="parseRow">
<xsl:with-param name="rowContents"
select="substring-before($catContents,'~!~')"/>
<xsl:with-param
name="font-size" select="$font-size"/>
</xsl:call-template>
<xsl:call-template name="parseRows">
<xsl:with-param name="catContents"
select="substring-after($catContents,'~!~')"/>
<xsl:with-param
name="font-size" select="$font-size"/>
</xsl:call-template>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$catContents"/>
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template name="parseRow">
<xsl:param name="rowContents"/>
<xsl:param name="font-size" select="'-1'"/>
<tr>
<xsl:for-each select="xalan:tokenize($rowContents,'~')">
<td><font
size="{$font-size}"><xsl:value-of select="."/></font></td>
</xsl:for-each>
</tr>
</xsl:template>
This code works, but I'm thinking of modifying it. I know
that some xslt
engines use tail recursion to optimise their processing and
I'm worried
about breaking that.
1. Which xslt engines use tail recursion?
2. I'm not exactly sure about tail recursion. Does my xslt
above already
violate that? If not, what should I be careful about.
3. Is there a way for me to empirically test whether an xslt
engine uses
tail recursion?
I-Lin Kuo, Ann Arbor, MI
Macromedia Certified ColdFusion 5.0 Advanced Developer
Sun Certified Java 2 Programmer
Ann Arbor Java Users Group (www.aajug.org) SUN Top 25 JUG
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