the XPath 'for' statement, returns ???

mphare · January 28th, 2011, 06:10 PM

I must be reading XPath 2.0 incorrectly.

It seems that the statement:

Code:

for $i in 1 to 10 return $i

would return a sequence of the numbers from 1 to 10.
But putting that in a variable:

Code:

<xsl:variable name="temp">
   <xsl:sequence select="for $i in 1 to 10 return $i"/>
<xsl:/variable>

<xsl:for-each select="$temp">
   <xsl:value-of select="."/>
</xsl:for-each>

is not giving me what I wanted: access to each of the members of the sequence created from 1 to 10.

Now, for my purpose, this may be moot as I may be able to use

Code:

<xsl:for-each select="1 to 10">
   <xsl:value-of select="."/>
</xsl:for-each>

and accomplish my goal. But I thought I was on to something with the results of the for/in/to/return statement being put in a variable.

Having it in a variable might be nice so I could pass the sequence around to other functions or templates.

Did I leave something out, or is it just the wrong application/purpose of the for/in/to/return construct?

Thanks,

mhkay · January 28th, 2011, 06:47 PM

Using <xsl:value-of> as a child of <xsl:variable> is a bad (and very common) coding habit. It often has the desired effect, but not always, and only at great expense. Using xsl:sequence is better, but still wrong unless you use the "as" attribute to indicate the required type. Most of the time, it should be replaced by use of the select attribute:

Code:

<xsl:variable name="var" select="for $i in 1 to 10 return $i"/>

which of course can be further simplified to

Code:

<xsl:variable name="var" select="1 to 10"/>

What's happening is that when xsl:variable has no select attribute, and contained instructions (and no "as" attribute) it creates a temporary XML document. Documents are text, so the sequence of integers is converted to a string "1 2 3 4 5 6 7 8 9 10" which is not at all what you want. If you need to use child instructions to construct the value you can say as="xs:integer*", which overrides the default behaviour of creating an XML document.

mphare · January 28th, 2011, 06:58 PM

Nice! I caught myself using value-of and changed it to sequence, but ti didn't change the result. Using the select statement gave me exactly what I was looking for.

Thanks!