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Re: xpath expression restriction

Subject: Re: xpath expression restriction
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Fri, 04 Mar 2011 08:48:02 +0000
Re:  xpath expression restriction
On 04/03/2011 08:10, ac wrote:
Hi Mukul,

It works with the braces.
Still I wonder why it did not pick the "if" and evaluate it?

The grammar requires the operand of "gt" to be a RangeExpr, and a conditional expression is not a RangeExpr.

If a conditional expression were allowed here, it would create (more) confusion over expressions such as

3 gt if (a) then 2 else 3 + 5

Personally I would have preferred a self-closing conditional expression, like Algol-68's

if c then a else b fi

but the WG was convinced it was better to repeat the mistakes of the past in the interests of familiarity.

Michael Kay

I am not sure if I understand your question right, but
In the example, $cond is only checking for empty (null) or not.
In the code, it is more like
if ($logging or ($logged and string($nxtid))) then 1 else 0
also, abc is a sequence closer to
and the idea is simply to not copy the first element, under some condition
also, it is not really an xsl:copy-of, but an xsl:sequence ...

Thank you.


Hi Andre,
      I'm not sure, but perhaps writing the whole if condition in
braces may force evaluation of the if expression before providing this
operand to operator "gt".

i.e could you please try if following works,

<xsl:copy-of select="abc[position() gt (if ($cond) then 1 else 0)]"/>

also curious to know, what do you write to evaluate $cond?

On Fri, Mar 4, 2011 at 11:22 AM, ac<ac@xxxxxxxxxxxxx> wrote:

There must be a reason why I can write

<xsl:variable name="x" select="if ($cond) then 1 else 0"/>
<xsl:copy-of select="abc[position() gt $x]"/>

but not

<xsl:copy-of select="abc[position() gt if ($cond) then 1 else 0]"/>

What is the reason?  Is there any way to avoid having to declare the

Thank you,


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