Recently, working on completely different thing, I've realized that one may create a "generator", function returning different values per each call. I was somewhat puzzled with this conclusion, as I thought xslt functions have no side effects, and for the same arguments xslt function returns the same result.

I've confirmed the conclusion at the forum. See Scope of uniqueness of generate-id().

In short:

• each node has an unique identity;
• function in the course of work creates a temporary node and produces a result depending on identity of that node.

Example:

<xsl:stylesheet version="2.0"
  xmlns:f="data:,f"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">
  <xsl:message select="
    for $i in 1 to 8 return
      f:fun()"/>
</xsl:template>

<xsl:function name="f:fun" as="xs:string">
  <xsl:variable name="x">!</xsl:variable>

  <xsl:sequence select="generate-id($x)"/>
</xsl:function>

</xsl:stylesheet>

The next thought was that if you may create a generator then it's easy to create a good random number generator (that's a trivial math task).

Hey gurus, take a chance!