I have a requirement where I need to transform some XML into a different format. During this conversion I need to perform some calculations on some elements and return the calculated value into a new element in my transformed xml.

The problem is that some elements may not occur in my source xml and if they do not occur then I need to do the processing without them.

Here is an example;

I could have a car to finance with the following elements.
<CASHPRICE>12000.00</CASHPRICE>
<DEPOSIT>100.00</DEPOSIT>
<PARTEXCHANGE>100.00</PARTEXCHANGE>
<SETTLEMENTAMOUNT>100.00</SETTLEMENTAMOUNT>

I need to workout the effective deposit as a percentage of the cash price in my new xml.
<DEPOSITPERCENTAGE> = (DEPOSIT + PARTEXCHANGE - SETTLEMENTAMOUNT) / CASHPRICE

The deposit, partexchange and settlementamount elements may not always appear in the source xml and I need a way of performing the calculation conditionally if these elements do not exist.

I thought a series of for-each select statements and then <xsl:when test="DEPOSIT[. != 0] and PARTEXCHANGE[. != 0] and SETTLEMENTAMOUNT[. != 0]">

Does anyone have any other ideas how to approach this problem?

I do see one problem that might occur where if either some / all of these conditions are true then you would get the calucation being fired more than once.

Thanks for any pointers.

Declare variables whose value is initialized to that of the element if it is present, or the default value otherwise; then perform the calculation on the variables.

In 2.0 this is easy:

<xsl:variable name="discount" select="(DISCOUNT, 0)[1]"/>

In 1.0 it's a bit more convoluted:

<xsl:variable name="discount">
 <xsl:choose>
 <xsl:when test="DISCOUNT"><xsl:value-of select="DISCOUNT"/></xsl:when>
 <xsl:otherwise>0</xsl:otherwise>
</xsl:variable>

or you can cheat if you want (but it's horrible):

<xsl:variable name="discount" select="number(concat('0', DISCOUNT))"/>



Michael Kay
http://www.saxonica.com/

Thanks, this was handy for me as well. You did forget to close the choose condition though.

Shane C