variables in predicates

barski · August 1st, 2007, 05:22 PM

can someone explain to me why these produce two different outcomes
<p>Direct produces the correct result
<p>Variable does not

i thought variables were allowed in predicates

Code:

    <xsl:variable name="avariable">somenode</xsl:variable>

    <p>Direct: <xsl:value-of select="count(//*[somenode != 0])" /></p> 
    <p>variable: <xsl:value-of select="count(//*[$avariable != 0])" /></p>

mhkay · August 1st, 2007, 05:46 PM

Yes, variables are allowed in predicates.

Your first expression
<xsl:value-of select="count(//*[somenode != 0])" /></p>

means "count the number of element nodes in the document that have a child element called "somenode" whose string value, converted to a number, is not equal to zero"

Your second expression
<xsl:value-of select="count(//*[$avariable != 0])" /></p>

means "if the value of $avariable is not equal to zero (which is true, because it is equal to the string "somenode") then count the number of nodes in the document, otherwise return zero"

The two expressions are both valid, but they couldn't have more different meanings.

I think you're making the mistake of thinking that variables represent textual pieces of an expression, like variables in a macro language or in some shell script languages. They don't - they represent values.

Michael Kay
http://www.saxonica.com/
Author, XSLT Programmer's Reference and XPath 2.0 Programmer's Reference

barski · August 2nd, 2007, 09:59 AM

with some help of predicates within predicates http://www.ecos.sourceware.org/ml/xs.../msg00522.html

i was able to get done what i needed or it appears so... still have a few more things to test [anothernode=$x and *[name()=$avariable and . != 0]]

i have bought numerous books over the last decade and taught myself
vb6,c#,java,php,c++,sql and a few other languages along with "design theory" as it pertains to oop principles, patterns etc... and would consider myself pretty good in all those except c++ which i'm still learning. However, with this stuff the concepts run so counter to my intuition that it is really frustrating. Not giving up but after dealing with various transformation issues over the last couple of weeks i had to vent a little bit.