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Re: The operator '!=' returns false when one operand d

Subject: Re: The operator '!=' returns false when one operand doesn't exist
From: "Vasu Chakkera" <vasucv@xxxxxxxxxxx>
Date: Wed, 07 Aug 2002 18:02:08 +0000
xsl operand
The spec says so.. :)
This is the very reason why it is best advised not to use '!=' unless u are 100% sure what you want to do.You should instead use *not* ..
as in **not($x = 'text')**as opposed to **$x != 'text'**
the former is most likely to mean the intended meaning.
Vasu



From: Jerome Louvel <jerome_louvel@xxxxxxxx>
Reply-To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
To: XSL-List@xxxxxxxxxxxxxxxxxxxxxx
Subject: The operator '!=' returns false when one operand doesn't exist
Date: Wed, 7 Aug 2002 08:32:17 -0700 (PDT)


Hi All,

We have an issue with the XPath '!=' operator that has
a strange behavior when one of its operand doesn't
exist in the instance document. It returns 'false"
when you would expect "true" or some kind of exception
to be raised.

Sample stylesheet:
------------------
<?xml version="1.0" encoding="UTF-8"?>
<xsl:transform version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
	<xsl:template match="/">
		<data>
			<xsl:value-of select="/data/a != /data/b"/>
		</data>
	</xsl:template>
</xsl:transform>

Instance:
---------
<?xml version="1.0"?>
<data>
	<a>10</a>
</data>

This transformation will return 'false'.
If you add <b>11</b> under element a, or even an empty
<b/>, the result is becoming 'true'.

Could somebody explain me why we get such a result
(with MSXML 4.0 as well as Xalan)?
Is there a simple way, extension function or XPath
expression to would make this work as "expected" (true
is one of this operand doesn't exist)?

Thanks for your help!
Jerome.



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