Why do we return to this theme again?

Well, it's itching!

In cobolxom there is an utility function to allocate names in scope. Its signature looks like this:

<!--
  Allocates unique names in the form $prefix{number}?.
  Note that prefixes may coincide.
    $prefixes - a name prefixes.
    $names - allocated names pool.
    $name-max-length - a longest allowable name length.
    Returns unique names.
-->
<xsl:function name="t:allocate-names" as="xs:string*">
  <xsl:param name="prefixes" as="xs:string*"/>
  <xsl:param name="names" as="xs:string*"/>
  <xsl:param name="name-max-length" as="xs:integer?"/>

We have created several different implementations (all use recursion). Every implementation works fair for relatively small input sequences, say N < 100, but we have cases when there are about 10000 items on input. Algorithm's worst case complexity, in absence of associative containers, is O(N*N), and be sure it's an O-o-o-oh... due to xslt engine implementation.

If there were associative containers with efficient access (complexity is O(LogN)), and construction of updated container (complexity is also O(LogN)) then implementation would be straightforward and had complexity O(N*LogN).