Re: [xsl] An XPath expression that avoids writing special case code?

["Andre Cusson akhu01@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Hi Martin,
I really like your solution.
Short, elegant, and to the point.
The empty element is part of every set.
Changing a single character.
A piece of beauty & smarts.
Thank you.
Cheers,
ac


Le jeu. 17 juin 2021 C  10:16, Michael Kay mike@xxxxxxxxxxxx <
xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> a C)crit :

> This is a case for pipelines. First run a transformation that turns your
> document into something that better represents thet semantics, like
>
> <airports>
>   <airport>LHR</airport>
>   <airport>LAX</airport>
> </airports>
>
> and then do your actual query against this document.
>
> This gives you separation of concerns, and the first transformation in the
> pipeline is reusable code, you can use it regardless what query the second
> stage needs to perform.
>
> When you're dealing with data that originates from spreadsheets, where you
> often have to deal with complexities like rowspans and columnspans, this
> pipeline approach is the only way to preserve your sanity.
>
> Michael Kay
> Saxonica
>
> > On 17 Jun 2021, at 15:06, Roger L Costello costello@xxxxxxxxx <
> xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hi Folks,
> >
> > My XML document contains a bunch of <Row> elements, like so:
> >
> > <Document>
> >    ...
> >    <Row>
> >        <Cell>
> >            <Data>airport</Data>
> >        </Cell>
> >        <Cell>
> >            <Data>airports</Data>
> >        </Cell>
> >    </Row>
> >    ...
> > </Document>
> >
> > I want to fetch the Row whose Cell[1]/Data is 'airport' and whose
> Cell[2]/Data is 'airports'. So I created this XPath expression:
> >
> > /Document/Row[Cell[1]/Data eq 'airport'][Cell[2]/Data eq 'airports']
> >
> > I do this kind of fetching operation often, so I created a function to
> fetch the desired Row:
> >
> > <xsl:function name="f:getRow">
> >    <xsl:param name="element"/>
> >    <xsl:param name="parent"/>
> >    <xsl:sequence select="$document/Row[Cell[1]/Data eq
> $element][Cell[2]/Data eq $parent]" />
> > </xsl:function>
> >
> > I call the function this way:
> >
> > <xsl:sequence select="f:getRow('airport', 'airports')" />
> >
> > Sometimes there is an element that doesn't have a parent. That is,
> sometimes I'd like to fetch a Row in which Cell[2] is empty, like this:
> >
> >    <Row>
> >        <Cell>
> >            <Data>aviation</Data>
> >        </Cell>
> >        <Cell/>
> >    </Row>
> >
> > Then this call to f:getRow fails:
> >
> > <xsl:sequence select="f:getRow('aviation', '')" />        <!-- Those are
> two apostrophes within the parentheses -->
> >
> > Clearly I need to modify f:getRow. I could add special case code to test
> $parent to see if it is empty (the '' string) and do one thing, and if it's
> not empty do another thing. But I wonder if there is a more elegant
> solution that doesn't involve special case code? Is there a way to modify
> the XPath expression in f:getRow such that it fetches the correct Row
> regardless of whether $parent is empty or not?
> >
> > /Roger