I came up against a strange problem. How can I assign a value to a variable or parameter in a loop?

I need to check the value of a parameter or variable to decide whether to write a Cell or not like this:

<xsl:if test="$writeCell != 'no'">
    <Cell ss:MergeDown="number({$colgrps}-1)"/>
</xsl:if>

I only need to write it the first time in the loop(recursion). But when I go to the <xsl:otherwise> section of my code I need to pass a yes value so that the Col template can write this Cell instead of the curent template.

How can I do that in xslt 1 ?

Cheers

XSLT

<xsl:template match="ColGrp" mode="Header">
<xsl:param name="depth"/>

<xsl:if test=" ColGrp ">
  <xsl:param name="writeCell select="'yes'"/>
  <Row>

  <xsl:if test="$writeCell='yes'">
     <Cell ss:MergeDown="number({$colgrps}-1)"/>
  </xsl:if>

  <xsl:for-each select="//ColGrp[count(ancestor::ColGrp)=$depth]">
    <Cell ss:MergeAcross="{count(.//Col)*$msrs}" ss:StyleID="s24">
          <xsl:value-of select="@heading"/>
    </Cell>
  </xsl:for-each>
 </Row>
</xsl:if>
<xsl:choose>
 <xsl:when test="ColGrp">
   <xsl:apply-templates select="ColGrp[1]" mode="Header">
     <xsl:with-param name="depth" select="$depth+1"/>
     <xsl:with-param name="writeCell " select="'no'"/>
   </xsl:apply-templates>
 </xsl:when>
 <xsl:otherwise>
   <xsl:apply-templates select="Col[1]" mode="colHead">
     <xsl:with-param name="writeCell" select="'yes'"/>
   </xsl:apply-templates>
 </xsl:otherwise>
</xsl:choose>
</xsl:template>

XSLT is a declarative or functional language, not a procedural language, so there is no defined order of execution, and therefore no update of variables. Seems strange at first and it requires a different way of thinking about your problem, but you end up writing much better code as a result.

Questions like this always remind me of the COBOL programmers who used to ask "how do I achieve this without a GOTO statement"? Once you start thinking in a declarative functional way, the question never occurs to you.

Rather than looking at your procedural code and trying to reverse engineer it, I would suggest you try describing your problem: what is the output to be, as a function of the input? Try to describe the relationship of one to the other without describing a procedure for doing the work. Then you should find that this description translates very naturally into a functional program.



Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

thanks again Michael,

Sorry if I did not explain the problem well. Also, I sort of understand what you are saying when you mention that xslt is a declarative or functional language but would appreciate if you could clarify that to me.

With that in mind I tried to use lots of templates in the stylesheet instead of having just one template with lots of <for-each> loops. This is what I have done:

This template is the start. It calls the Columns template like this: <xsl:apply-templates select="Columns"/>

<xsl:template match="Report">
  <Workbook>
   <xsl:variable name="colspanHead" select="number($msrs+$cols)"/>
   <xsl:variable name="rowspanFirstCell" select="number($msrs)-1"/>
   <Worksheet>
   <xsl:attribute name="ss:Name"><xsl:value-of select="'Audit'"/></xsl:attribute>
   <Table x:FullColumns="1" x:FullRows="1">
      <xsl:apply-templates select="Columns"/>
   </Table>
  </Worksheet>
</Workbook>
</xsl:template>

This template calls the ColGrp template with mode = "header" and passes a parameter depth. Most of the time this parameter will be 1.


<xsl:template match="Columns">
  <xsl:apply-templates select="ColGrp[1]" mode="Header">

  <xsl:with-param name="depth">
  <xsl:choose>
   <xsl:when test="$axisHeads='true'">
    <xsl:value-of select="0"/>
   </xsl:when>
   <xsl:otherwise>
     <xsl:value-of select="1"/>
   </xsl:otherwise>
</xsl:choose>
</xsl:with-param>
</xsl:apply-templates>
</xsl:template>

Here is where I will have to decide whether to add the first Cell or not.
first I check to see if I have a ColGrp child node <xsl:if test=" ColGrp "> then
I have to decide whether to add a Cell with a rowspan or not. The test should be something like this:
 <xsl:if test="insertCellWithRowSpan=true">
      <Cell ss:MergeDown="number({$colgrps}-1)"/>
 </xsl:if>

Then I check if I have another ColGrp child node <xsl:when test="ColGrp">
and call the same template again
<xsl:apply-templates select="ColGrp[1]" mode="Header">
<xsl:with-param name="depth" select="$depth+1"/>
<xsl:with-param name="insertCellWithRowSpan"/>

</xsl:apply-templates>

But this time I cannot output the first Cell with the rowspan again and I do not know how to achieve that. Also, if this test is not true <xsl:when test="ColGrp">
I have to call the Col template passing a parameter so that I can output the first Cell in that template.


<xsl:template match="ColGrp" mode="Header">
  <xsl:param name="depth"/>

  <xsl:param name="insertCellWithRowSpan"/>

  <xsl:if test=" ColGrp ">
  <Row>
    <xsl:if test="insertCellWithRowSpan='yes'">
      <Cell ss:MergeDown="number({$colgrps}-1)"/>
    </xsl:if>

    <xsl:for-each select="//ColGrp[count(ancestor::ColGrp)=$depth]">
    <Cell ss:MergeAcross="{count(.//Col)*$msrs}" ss:StyleID="s24">
      <xsl:value-of select="@heading"/>
    </Cell>
    </xsl:for-each>
</Row>
</xsl:if>
<xsl:choose>
<xsl:when test="ColGrp">
<xsl:apply-templates select="ColGrp[1]" mode="Header">
  <xsl:with-param name="depth" select="$depth+1"/>
  <xsl:with-param name="insertCellWithRowSpan" select="'no'"/>
</xsl:apply-templates>
</xsl:when>
<xsl:otherwise>
<xsl:apply-templates select="Col[1]" mode="colHead">
  <xsl:with-param name="insertCellWithRowSpan" select="'yes'"/>
</xsl:apply-templates>
</xsl:otherwise>
</xsl:choose>
</xsl:template>



<xsl:template match="Col" mode="colHead">
  <xsl:param name="insertCellWithRowSpan"/>
  <xsl:variable name="countRowSpan">
     <xsl:value-of select="number($msrs)-1"/>
  </xsl:variable>
<Row>
<xsl:for-each select="ancestor::Columns//Col">
  <xsl:if test="position()=1 and $insertCellWithRowSpan='yes'">
    <Cell ss:MergeDown="{$colgrps}"/>
  </xsl:if>
    <Cell ss:MergeAcross="{$countRowSpan}" ss:StyleID="s24">
      <xsl:value-of select="@heading"/>
    </Cell>
</xsl:for-each>
</Row>
<Row>
<xsl:for-each select="//Col">
<xsl:apply-templates select="//Measures">
  <xsl:with-param name="pos" select="position()"/>
</xsl:apply-templates>
</xsl:for-each>
</Row>
</xsl:template>


<xsl:template match="//Measures">
 <xsl:param name="pos"/>
  <xsl:choose>
   <xsl:when test="position()=1 and $pos=1">
     <Cell ss:Index="2" ss:StyleID="s27">
        <xsl:value-of select="@heading"/>
     </Cell>
   </xsl:when>
   <xsl:otherwise>
    <Cell ss:StyleID="s27" >
      <xsl:value-of select="@heading"/>
   </Cell>
  </xsl:otherwise>
</xsl:choose>
</xsl:for-each>
</xsl:template>

However, I am stuck and would appreciate if you could help me to find a solution for that.

XML

<Report xmlns="">
<Measures>
  <Measure idx="1" heading="Total Pages"/>
  <Measure idx="2" heading="Cost"/>
</Measures>
  <Columns>
    <ColGrp heading="Company Name">
      <ColGrp heading="Test Corporation">
        <Col heading="Test A" />
      </ColGrp>
    </ColGrp>
  </Columns>
</Report>

>Also, I sort of understand what you are saying when you mention that xslt is a declarative or functional language but would appreciate if you could clarify that to me.

Then you should read my book. I try very hard there to explain the fundamental concepts.

You've shown me a lot of code, which I don't really have time to read: but you haven't explained the problem you are trying to solve, which is what I asked for.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

Hi Michael,

I have already read your book. That is why I am using lots of templates instead of only using the <xsl:for-each> construction as I used to do in the past.

I have to create a padding cell only once either when I am in the ColGrp template or in the Col template.

If I create it in the ColGrp template then I cannot create it again in the Col template.

If there is only one CooGrp in the xml I jump straight to the Col template and therefore have to create the cell in there.

Also, If I create it in the ColGrp template and I have more than one ColGrp in the xml I cannot create it again when I recurse to the next ColGrp. I think I have to find a way to condition the caller.

I am trying to generate a 3 dimension table based on a xml that can change. I may have only one ColGrp or many ColGrp. My xslt works for when I have only one ColGrp.

Only one ColGrp

<?xml version="1.0"?>
<Report xmlns="">
  <Measures>
    <Measure idx="1" heading="Total Pages"/>
    <Measure idx="2" heading="Cost"/>
  </Measures>
  <Columns>
    <ColGrp heading="Year">
      <Col heading="2003"/>
      <Col heading="2004"/>
    </ColGrp>
  </Columns>
......

More than one ColGrp

<Report xmlns="">
<Measures>
  <Measure idx="1" heading="Total Pages"/>
  <Measure idx="2" heading="Cost"/>
</Measures>
  <Columns>
    <ColGrp heading="Company Name">
      <ColGrp heading="Test Corporation">
        <Col heading="Test A" />
      </ColGrp>
    </ColGrp>
  </Columns>
............
</Report>


                               2003 2004
                  Total Pages Cost Total Pages Cost
Gastroenterology 42.00 64,230.00
General Medicine 36.00 $222,490.00
Orthopedics 44.00 $107,400.00
Other Specialty 36.00 $35,820.00
Pharmacy 14.20 $128,030.00
Rheumatology 60.00 $125,520.00

Cheers