Testing type of a param

A param's type can be any of

  string, number, boolean, node-set

Within a called template I'd like to be able use <xsl:choose> to 
branch based on whether a parameter is a node-set or not.

Is there a way to do this?

FYI, here is the template I'm trying to write; it is a general 
purpose repeat function:

<!--
  This template takes two parameters:
    value - the thing to repeat.
    n - the number of times to repeat it to the result tree.
  If value is a node set, xsl:copy-of is used.
  If value is a simple value, xsl:value-of is used.
  -->
<xsl:template name="repeat">
  <xsl:param name="value"/>
  <xsl:param name="n"/>
  <xsl:if test="$n != 0">
    <xsl:choose>
      <xsl:when test="?"> 
        <!-- value is a node set, use copy-of -->
        <xsl:copy-of select="$value"/>
      </xsl:when>
      <xsl:otherwise>
        <!-- value is a simple type, use value-of -->
        <xsl:value-of select="$value"/>
      </xsl:otherwise>
    </xsl:choose>
    <xsl:call-template name="repeat">
      <xsl:with-param name="n" select="$n - 1"/>
      <xsl:with-param name="value" select="$value"/>
    </xsl:call-template>
  </xsl:if>
</xsl:template>

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