> On 9 Jul 2021, at 14:03, Roger L Costello costello@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Michael Kay wrote:
>
>> In this situation, you can use grouping:
>>
>> <xsl:for-each-group select="row" group-by="x, y" composite="yes">
>>    <xsl:sequence select="current-group()[1]"/>
>> </xsl:for-each>
>
> That is a beautiful solution.
>
> Just curious, what is the time complexity of that loop in Saxon? Is Saxon
able to do in in better than O(n**2)?
>

O(n log n).

group-by is implemented using a hash table.

Michael Kay
Saxonica