123: fn:duplicate-values

[ChristianGruen]

I decided to create a PR for the initial proposal of this function, as I came across at least two other use cases for it since the issue was created.

I believe that the group by clause is the best choice for more complex operations, such as advanced comparisons or creating histograms.

[michaelhkay]

It's unfortunate that the function cannot, in fact, be implemented using a FLWOR group-by clause, as that does not support dynamic collations. Perhaps it would be better to provide an XSLT implementation:

<xsl:for-each-group select="$values" group-by="." collation="{$collation}">
  <xsl:sequence select="current-group()[2]"/>
</xsl:for-each>

(although this differs in that the result is more strictly defined; to be precisely equivalent, you would want to randomise the order of the input).

[ChristianGruen]

Perhaps it would be better to provide an XSLT implementation:

Added, thanks.

[ChristianGruen]

The example has been fixed; I’m optimistic this can be merged.

[ndw]

The CG agreed to merge this PR at meeting 042.