[xsl] How can I achieve correct tail-recursion ?

[Frédéric Schwebel <Fred.Schwebel@xxxxxxxxxxx>]

Hello, I'm using SaxonHE 9.2 with a layout sheet for braille output. I
need to process every child of node "doc" while remembering line and
page numbers for each child I process. Here's the sub-part of the
sheet ("doc" is the root of my document) :
----------------
[...]
<xsl:template match="doc">
	<xsl:apply-templates select="@*" />
	<xsl:call-template name="miseEnPage"/>
</xsl:template>

<!-- TEMPLATE PRINCIPAL DE MISE EN PAGE -->
<xsl:template name="miseEnPage">
	<xsl:param name="numNoeud" as="xs:integer" select="1" />
	<xsl:param name="numPage" as="xs:integer" select="1" />
	<xsl:param name="numLigne" as="xs:integer" select="1" />

	<xsl:variable name="texteMisEnPage" as="xs:string*">
		<xsl:choose>
			<!-- saut de page -->
			<xsl:when test="*[$numNoeud][self::page-break]">
				<xsl:value-of
select="translate(doc:sautePage(true(),$numLigne,$numPage),concat($sautAGener
er,$espace),'&#10;&pt;')"/>
			</xsl:when>
			<xsl:when test="not(string(*[$numNoeud]))"><!-- le fils est vide -->
				<xsl:call-template name="gestionLignesVides">
					<xsl:with-param name="numNoeud" select="$numNoeud" />
					<xsl:with-param name="numLigne" select="$numLigne" />
					<xsl:with-param name="numPage" select="$numPage" />
				</xsl:call-template>
			</xsl:when>
			<xsl:when test="*[$numNoeud][self::ul or self::ol]"> <!-- liste ` puces
-->
				<xsl:call-template name="MEPliste">
					<xsl:with-param name="noeud" select="*[$numNoeud]" />
					<xsl:with-param name="numPage" select="$numPage" tunnel="yes"/>
					<xsl:with-param name="numLigne" select="$numLigne" tunnel="yes" />
				</xsl:call-template>
			</xsl:when>
[... other xsl:when ...]
			<xsl:otherwise><xsl:text></xsl:text></xsl:otherwise>
		</xsl:choose>
	</xsl:variable>

	<!-- ******** affichage du texte ********* -->
	<xsl:variable name="texteMisEnPageJoint"
select="string-join($texteMisEnPage,'')" as="xs:string" />
	<xsl:value-of select="$texteMisEnPageJoint" />

	<xsl:variable name="nouvPage" as="xs:integer"
select="doc:nouvellePage($texteMisEnPageJoint,$numPage)" />
	<xsl:variable name="nouvLigne" as="xs:integer"
select="doc:nouvelleLigne($texteMisEnPageJoint,$numLigne)" />

<!-- here comes the tail recursion -->
	<xsl:if test="$numNoeud &lt; count(*)">
		<xsl:call-template name="miseEnPage">
			<xsl:with-param name="numNoeud" select="$numNoeud+1" />
			<xsl:with-param name="numPage" select="$nouvPage" />
			<xsl:with-param name="numLigne" select="$nouvLigne" />
		</xsl:call-template>
	</xsl:if>
	<xsl:if test="$mise_en_page and ($numNoeud = count(*))"> <!-- appel
final pour num de page et saut de page -->
		<xsl:variable name="completeLastPage" as="xs:string"
select="doc:sautePage(true(),$nouvLigne,$nouvPage)" />
		<xsl:value-of
select="translate($completeLastPage,concat($sautAGenerer,$espace),'&#10;&pt;'
)"
/>
	</xsl:if>
</xsl:template>

----------------------------------
I've read Saxon optimizes tail recursion as an iterating function,
this would mean no stack overflow.
I switched back to Saxon 9.1 and tried to achieve this with
saxon:iterate and parameters :
---------------------------------
<xsl:template name="miseEnPage">

	<saxon:iterate select="*" xmlns:saxon="http://saxon.sf.net/";
xsl:extension-element-prefixes="saxon">
		<xsl:param name="numPage" as="xs:integer" select="1" />
		<xsl:param name="numLigne" as="xs:integer" select="1" />

		<xsl:variable name="texteMisEnPage" as="xs:string*">
			<xsl:choose>
				<!-- saut de page -->
				<xsl:when test="self::page-break">
					<!--<xsl:message select="OUI"/>-->
					<xsl:value-of
select="translate(doc:sautePage(true(),$numLigne,$numPage),concat($sautAGener
er,$espace),'&#10;&pt;')"/>
				</xsl:when>
				<xsl:when test="not(string(.))"><!-- le fils est vide -->
					<xsl:call-template name="gestionLignesVides">
						<xsl:with-param name="numLigne" select="$numLigne" />
						<xsl:with-param name="numPage" select="$numPage" />
					</xsl:call-template>
				</xsl:when>
				<xsl:when test="self::ul or self::ol"> <!-- liste ` puces -->
					<xsl:call-template name="MEPliste">
						<xsl:with-param name="numPage" select="$numPage" tunnel="yes"/>
						<xsl:with-param name="numLigne" select="$numLigne" tunnel="yes" />
					</xsl:call-template>
				</xsl:when>
[... other xsl:when ...]
				<xsl:otherwise><xsl:text></xsl:text></xsl:otherwise>
			</xsl:choose>
		</xsl:variable>

		<!-- ******** affichage du texte ********* -->
		<xsl:variable name="texteMisEnPageJoint"
select="string-join($texteMisEnPage,'')" as="xs:string" />
		<xsl:value-of select="$texteMisEnPageJoint" />

		<saxon:continue>
			<xsl:with-param name="numPage" as="xs:integer"
select="doc:nouvellePage($texteMisEnPageJoint,$numPage)" />
			<xsl:with-param name="numLigne" as="xs:integer"
select="doc:nouvelleLigne($texteMisEnPageJoint,$numLigne)" />
		</saxon:continue>
	</saxon:iterate>
	<!-- <xsl:value-of
select="concat('nouvpage',$nouvPage,'nouvligne',$nouvLigne,'matches ',
string($pagesEnPlus),' ',string($lignesEnPlus))" /> -->
</xsl:template>

-----------------------------------

With saxon:iterate , no more stack overflow and processing is about
10x faster ! I suppose I would get a nearby result if my first sheet
did correct tail recursion. How can I modify it to do correct tail
recursion ? I couldn't find any doc about it on the W3C website, nor
on saxonica.com, nor on http://saxon.markmail.org/.

Thanks for any help,
Regards
Fridiric Schwebel
http://sourceforge.net/projects/nat-braille/