RE: [xsl] tail recursion optimization (was How efficient is DVC?)

["Michael Kay" <mhk@xxxxxxxxx>]

> The problem that when the recursive template is a matching 
> template instead of a named template, it is hard for the 
> processor to recognize that the apply-templates at the end of 
> the template will result in the same template being applied. 
> For example, Robert's second example has this:
> 
>   <xsl:template match="group">
>     <xsl:copy>
>       <xsl:copy-of select="@*"/>
>       <xsl:copy-of select="./city"/>
>     </xsl:copy>
>     <xsl:apply-templates select="./group"/>
>   </xsl:template>
> 
> I don't know if any processors can optimize this. 

It's true that Saxon today only does tail-recursion optimization on a
self-recursive call-template instruction. In principle, however, any
call done as the last thing in a routine can be optimized in this way,
it doesn't have to be a self-recursive call. So it's quite possible in
principle to optimize this one even if you can't recognize it as being
self-recursive.

Michael Kay


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