Re: [xsl] how to optimize recursive algorithm?

[David Tolpin <dvd@xxxxxxxxxxxxxx>]

> For instance, say you have a source document like this:
> 
> <top>
>     <a/>
>     <b/>
>     <c/>
>     <d/>
> </top>
> 
> and the output of "b" depends on the position of "a", "c" depends on "b" and
> so on.

Functional languages are good at expressing loops.

<xsl:template name="position">
 <!-- get results of previous computations via parameters -->
  <xsl:param name="prev-x"/><xsl:param name="prev-y"/>

 <!-- compute current values based on the current node and results computed for the previous one -->
  <xsl:variable name="x" select="$prev-x + @width"/>
  <xsl:variable name="y" select="$prev-y + @height"/>

 <!-- output the current node with the results computed -->
  <xsl:copy>
    <xsl:copy-of select="@*">
    <xsl:attibute name="x"><xsl:value-of select="$x"/></xsl:attribute>
    <xsl:attibute name="y"><xsl:value-of select="$y"/></xsl:attribute>
  </xsl:copy>

 <!-- call the template for the next sibling, if there is one -->
  <xsl:for-each select="following-sibling::*[1]">
    <xsl:call-template name="position">
      <xsl:with-param name="prev-x" select="$x"/>
      <xsl:with-param name="prev-y" select="$y"/>
    </xsl:call-template>
  </xsl:for-each>

</xsl:template>

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