XSLT 1.0 recursion - xslt

Question

I'm stuck with recursion, was wondering if anyone can help me out with it.
I have <Receipts> and <Deposits> elements, that are not verbose, i.e. that a <Receipts> element doesn't have an attribute to show what <Deposit> it is towards. I need to figure out <Deposits> "still amount due" and when a last receipt towards it was paid if any.
I'm trying to do it with the following code:
The idea was to take 1st deposit and see if there are receipts. If the deposit isn't fully paid and there are more receipts - call that recorsive function with all the same params except now count in following receipt.
If there aren't any more receipts or deposit is payed - process it correctly (add required attributes). Otherwise proceed with 2nd deposit. And so on.
However, the XSLT crashes with error message that "a processor stack has overflowed - possible cause is infinite template recursion"
I would really appreciate any help/teps... I'm not that great with recursion and can't understand why mine here doesn't work.
Thanks! :)
<!-- Accumulate all the deposits with #DueAmount attribute -->
<xsl:variable name="depositsClassified">
<xsl:call-template name="classifyDeposits">
<!-- a node-list of all Deposits elements ordered by DueDate Acs -->
<xsl:with-param name="depositsAll" select="$deposits"/>
<xsl:with-param name="depositPrevAmount" select="'0'"/>
<!-- a node-list of all Receipts elements ordered by ReceivedDate Acs -->
<xsl:with-param name="receiptsAll" select="$receiptsAsc"/>
<xsl:with-param name="receiptCount" select="'1'"/>
</xsl:call-template>
</xsl:variable>
<xsl:template name="classifyDeposits">
<xsl:param name="depositsAll"/>
<xsl:param name="depositPrevAmount" select="'0'"/>
<xsl:param name="receiptsAll"/>
<xsl:param name="receiptCount"/>
<xsl:if test="$depositsAll">
<!-- Do required operations for the 1st deposit -->
<xsl:variable name="depositFirst" select="$depositsAll[1]"/>
<xsl:variable name="receiptSum">
<xsl:choose>
<xsl:when test="$receiptsAll">
<xsl:value-of select="sum($receiptsAll[position() <= $receiptCount]/#ActionAmount)"/>
</xsl:when>
<xsl:otherwise>0</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:variable name="diff" select="$depositPrevAmount + $depositFirst/#DepositTotalAmount - $receiptSum"/>
<xsl:choose>
<xsl:when test="$diff > 0 and
$receiptCount < $receiptsQuantityOf">
<xsl:call-template name="classifyDeposits">
<xsl:with-param name="depositsAll" select="$depositsAll"/>
<xsl:with-param name="depositPrevAmount" select="$depositPrevAmount"/>
<xsl:with-param name="receiptsAll" select="$receiptsAll"/>
<xsl:with-param name="receiptCount" select="$receiptCount + 1"/>
</xsl:call-template>
</xsl:when>
<xsl:otherwise>
<!-- Record changes to the deposit (#DueAmount and receipt ReceivedDate) -->
<xsl:apply-templates select="$depositFirst" mode="defineDeposit">
<xsl:with-param name="diff" select="$diff"/>
<xsl:with-param name="latestReceiptForDeposit" select="$receiptsAll[position() = $receiptCount]"/>
</xsl:apply-templates>
<!-- Recursive call to the next deposit -->
<xsl:call-template name="classifyDeposits">
<xsl:with-param name="depositsAll" select="$depositsAll[position() > 1]"/>
<xsl:with-param name="depositPrevAmount" select="$depositPrevAmount + $depositFirst/#DepositTotalAmount"/>
<xsl:with-param name="receiptsAll" select="$receiptsAll"/>
<xsl:with-param name="receiptCount" select="'1'"/>
</xsl:call-template>
</xsl:otherwise>
</xsl:choose>
</xsl:if>
</xsl:template>
<!-- Determine deposit's status, due amount and payment received date if any -->
<xsl:template match="Deposits" mode="defineDeposit">
<xsl:param name="diff"/>
<xsl:param name="latestReceiptForDeposit"/>
<xsl:choose>
<xsl:when test="$diff <= 0">
<xsl:apply-templates select="." mode="addAttrs">
<xsl:with-param name="status" select="'paid'"/>
<xsl:with-param name="dueAmount" select="'0'"/>
<xsl:with-param name="receipt" select="$latestReceiptForDeposit"/>
</xsl:apply-templates>
</xsl:when>
<xsl:when test="$diff = ./#DepositTotalAmount">
<xsl:apply-templates select="." mode="addAttrs">
<xsl:with-param name="status" select="'due'"/>
<xsl:with-param name="dueAmount" select="$diff"/>
</xsl:apply-templates>
</xsl:when>
<xsl:when test="$diff < ./#DepositTotalAmount">
<xsl:apply-templates select="." mode="addAttrs">
<xsl:with-param name="status" select="'outstanding'"/>
<xsl:with-param name="dueAmount" select="$diff"/>
<xsl:with-param name="receipt" select="$latestReceiptForDeposit"/>
</xsl:apply-templates>
</xsl:when>
<xsl:otherwise/>
</xsl:choose>
</xsl:template>
<xsl:template match="Deposits" mode="addAttrs">
<xsl:param name="status"/>
<xsl:param name="dueAmount"/>
<xsl:param name="receipt" select="''"/>
<!-- Constract a new MultiDeposits element with required info -->
<xsl:copy>
<xsl:copy-of select="./#*"/>
<xsl:attribute name="Status"><xsl:value-of select="$status"/></xsl:attribute>
<xsl:attribute name="DueAmount"><xsl:value-of select="$dueAmount"/></xsl:attribute>
<xsl:if test="$receipt">
<xsl:attribute name="latestReceiptDate">
<xsl:value-of select="$receipt/#ActionDate"/>
</xsl:attribute>
</xsl:if>
<xsl:copy-of select="./*"/>
</xsl:copy>
</xsl:template>

Answer 1

Your named template classifyDeposits is definitely recursing infinitely. It has no base case. In the <xsl:choose> section you have two conditions: <xsl:when> and <xsl:otherwise>, however you call classifyDeposits in both conditions.
So no matter what you pass to this template, it will call itself. You need to have a base case: a condition in which the template doesn't call itself.
In pseudocode, you're essentially doing this:
function recursive
if (A>B) then
call recursive
else
call recursive
You need to add another branch, somewhere, that does not call itself.
function recursive
if (C=0) then
return
else if (A>B) then
call recursive
else
call recursive
Of course, just having the condition isn't good enough. It needs to be reachable.

Answer 2

One thing i've learned about concerning recursion is that you need to make sure that you have a condition that will trigger when you are done.
example:
decrement_me_until_zero(int i)
{
if(i ==0) return; //we're done here, roll on back up!
else
{
i = i-1;
decrement_me_until_zero(i);
return;
}
}
I don't know xlst at all, but this can be a simple reason why recursion can go into an infinite loop. Consider instead:
decrement_me_until_zero(int i)
{
if(i ==0) return; //we're done here, roll on back up!
else
{
decrement_me_until_zero(i);
i=i-1; //oops! we decrement after we pass the variable down!
return;
}
}
I hope that helps