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Re: [xsl] "Tunneling" a parameter in document order

Subject: Re: [xsl] "Tunneling" a parameter in document order
From: "G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 13 Apr 2012 13:01:53 -0400

At 2012-04-13 10:31 +0200, Christian Roth wrote:
I'll try in a different way: Imagine someone has laid a rope along the path of a depth-first traversal of the document tree. The initial color of the rope is red. However, any node in the tree may decide to change its color (e.g. to green), which the rope then has from the start of that node on for all later (=following::) ones until we reach the document end, or up to the next node that chooses to change the rope's color again.

Isn't the length of rope with the new colour just the current length of the rope less the length of the rope at the last time the colour changed?

Which new color a node changes the rope's color to depends on its context and(!) the current color of the rope it has when it reaches it.

Fine, but if the boundaries are detectable then the distance between boundaries is the document-origin position of the "current" boundary less the document-origin position of the previous boundary.

Could you do something like:

  <xsl:variable name="this" select="count( preceding::whatever[] )"/>
  <xsl:variable name="previous"
    select="count( preceding::boundary[1]/preceding::whatever[] )"/>
  <xsl:value-of select="$this - $previous"/>

... or something I don't like doing but it may be necessary because of the nature of the counting:

  <xsl:variable name="this">
    <xsl:number level="any" count="...whatever..."/>
  <xsl:variable name="previous">
    <xsl:number select="...location of previous..."
                level="any" count="...whatever..."/>
  <xsl:value-of select="number($this) - number($previous)"/>

That way you are not trying to count *just* what is the current colour in the rope ... you know how to count to the beginning, so just count to the beginning of both the current location and the previous boundary to get the count of the current colour.

I think it is the column spanning attribute of DocBook that I implement in XSLT/XSL-FO using the number of columns from the start of the table for the current column subtract the number of columns from the start of the table for the start of the span in order to get the number of columns of the span itself. When you described your rope analogy I immediately thought of the named column spanning in DocBook.

I hope this helps.

. . . . . . . . . . . Ken

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