Using an xsl param as argument to XPath function - xslt

Question

I've been trying to figure out a way to use a param/variable as an argument to a function.
At the very least, I'd like to be able to use basic string parameters as arguments as follows:
<xsl:param name="stringValue" default="'abcdef'"/>
<xsl:value-of select="substring(string($stringValue),1,3)"/>
The above code generates no output.
I feel like I'm missing a simple way of doing this. I'm happy to use exslt or some other extension if an xslt 1.0 processor does not allow this.
Edit:
I am using XSL 1.0 and transforming using Nokogiri, which supports XPATH 1.0 . Here is a more complete snippet of what I am trying to do:
I want to pass column numbers as parameters using nokogiri as follows
document = Nokogiri::XML(File.read('table.xml'))
template = Nokogiri::XSLT(File.read('extractTableData.xsl'))
transformed_document = template.transform(document,
["tableName","'Problems'", #Table Heading
"tablePath","'Table'", #Takes an absolute XPATH String
"nameColumnIndex","2", #column number
"valueColumnIndex","3"]) #column number
File.open('FormattedOutput.xml', 'w').write(transformed_document)
My xsl then wants to access every TD[valueColumnIndex] and and retrieve the first 3 characters at that position, which is why I am using a substring function. So I want to do something like:
<xsl:value-of select="substring(string(TD[$valueColumnIndex]),1,3)"/>
Since I was unable to do that, I tried to extract TD[$valueColumnIndex] to another param valueCode and then do substring(string(valueCode),1,3)
That did not work either (which is to say, no text was output, whereas <xsl:value-of select="$valueCode"/> gave me the expected output).
As a result, i decided to understand how to use parameters better, I would just use a hard coded string, as mentioned in my earlier question.
Things I have tried:
using single quotes around abcdef (and not) while
using string() around the param name (and not)
Based on the comments below, it seems I am handicapped in my ability to understand the error because Nokogiri does not report an error for these situations. I am in the process of installing xsltproc right now and seeing if I receive any errors.
Finally, here is my entire xsl. I use a separate template forLoop because of the valueCode param I am creating. The lines of interest are the last 5 or so. I cannot include the xml as there are data use issues involved.
<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:ext="http://exslt.org/common"
xmlns:dyn="http://exslt.org/dynamic"
exclude-result-prefixes="ext dyn">
<xsl:param name="tableName" />
<xsl:param name="tablePath" />
<xsl:param name= "nameColumnIndex" />
<xsl:param name= "valueColumnIndex"/>
<xsl:template match="/">
<xsl:param name="tableRowPath">
<xsl:value-of select="$tablePath"/><xsl:text>/TR</xsl:text>
</xsl:param>
<!-- Problems -->
<section>
<name>
<xsl:value-of select="$tableName" />
</name>
<!-- <xsl:for-each select="concat($tablePath,'/TR')"> -->
<xsl:for-each select="dyn:evaluate($tableRowPath)">
<!-- Encode record section -->
<xsl:call-template name="forLoop"/>
</xsl:for-each>
</section>
</xsl:template>
<xsl:template name="forLoop">
<xsl:param name="valueCode">
<xsl:value-of select="./TD[number($valueColumnIndex)][text()]"/>
</xsl:param>
<xsl:param name="RandomString" select="'Try123'"/>
<section>
<name>
<xsl:value-of select="./TD[number($nameColumnIndex)]"/>
</name>
<code>
<short>
<xsl:value-of select="substring(string($valueCode),1,3)"/>
</short>
<long>
<xsl:value-of select="$valueCode"/>
</long>
</code>
</section>
</xsl:template>
</xsl:stylesheet>

Answer 1

Use it this way:
<xsl:param name="stringValue" select="'abcdef'"/>
<xsl:value-of select="substring($stringValue,1,3)"/>