# Re: how to optimize recursive algorithm?

 Subject: Re: how to optimize recursive algorithm? From: David Tolpin Date: Thu, 27 Nov 2003 18:16:55 +0400 (AMT)
```> 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>

XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list

```

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