position() and last()

[Michael Kay]

A "for" expression does not change the focus (that is, the context item,
position, or size). This is a common mistake for anyone accustomed to
xsl:for-each - I make it frequently myself.

In XQuery (but not XPath) you can assign an extra variable to represent the
current position, thus:

for $i at $pos in $items return
($i, if ($pos = count($items)) then () else ",")

Alternatively you can iterate over the positions:

(for $n in 1 to count($items)-1 return ($items[$n], ",")), $items[last()])

In many cases (but not this one) the insertion of separators between items
can be achieved using the string-join function:

string-join($items, ',')

position() and last() are available in XQuery but they are only really
useful inside predicates.

Michael Kay
 

> -----Original Message-----
> From: http://xquery.com/mailman/listinfo/talk 
> [mailto:http://xquery.com/mailman/listinfo/talk] On Behalf Of R. Mark Volkmann
> Sent: 01 September 2004 04:15
> To: http://xquery.com/mailman/listinfo/talk
> Subject:  position() and last()
> 
> I know how to use these functions in XSLT, but I haven't 
> figured out how to
> use them in XQuery.
> For example, suppose I want to put a comma between items, but 
> not after the
> last one.
> I could do something like this.
> 
> for $i in $items
> return (
>   $i,
>   if (position() = last()) then () else ","
> )
> 
> This doesn't work. What am I doing wrong?
> 
> 
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