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Re: Xpath query to return "NULL" values?

From: David Carlisle <david-news@---------.-----.--.-->
To: NULL
Date: 6/5/2009 11:36:00 PM

Mario Splivalo wrote:
> Here is my XML document:
> 
> <a>
>   <b>1</b>
>   <b>2</b>
>   <b></b>
>   <b>3</b>
> </a>
> 
> When I execute this XPath query against it: /a/b/text()
> 
> I get only 1, 2 and 3:
> 
> mario@mike:~$ echo "<a><b>1</b><b>2</b><b></b><b>3</b></a>" | xpath -e '/a/b/@id'
> Found 3 nodes in stdin:
> -- NODE --
> 1
> -- NODE --
> 2
> -- NODE --
> 3
> mario@mike:~$ 
> 
> Is there a way to extract that NULL-valued node?
> 
> 	Mike

xpath doesn't have a NULL value, and text nodes never have an empty 
string as value. the third b has no child node at all.
It's actually rather rare to use text() in xpath, normally you'd just 
select the b nodes
the xpath /a/b  will select 4 b nodes with string values
"1" "2" "" "3"
In xpath 1 you can only have a node set so teh set of b nodes is the 
nearest you can get to this.
In xpath2 you could return the sequence of string values directly as
/a/b/string(.)

David

-- 
http://dpcarlisle.blogspot.com

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