I was trying to do something like:
def id(e: List[Int], acc: List[Int]): List[Int] =
if (e.isEmpty)
acc.reverse
else
id(e.tail, e.head :: acc)
or
<xsl:template match="@*|node()">
<xsl:copy>
<xsl:apply-templates select="@*|node()"/>
</xsl:copy>
</xsl:template>
But, I didn't figure how to pass anything analogous to "head" of an
element, or analagous to <xsl:copy/>.
If you can give an example of a tail recursive identity transformation
in XQuery that would be helpful to me.
Kendall
On 09/15/2017 02:23 AM, Michael Kay wrote:
I'm very confused by this. The function body contains two recursive calls. The
one inside the typeswitch is certainly not tail-recursive, so you're going to
get recursion depth equal to the maximum tree depth. The other call, as far as
I can see, merely returns its second argument unchanged, which seems totally
pointless.
Michael Kay
Saxonica
On 15 Sep 2017, at 09:30, Kendall Shaw <ks...@kendallshaw.com> wrote:
I don't remember seeing an xquery function that tries to return it's input
unchanged.
Can this be improved:
declare function local:id($e as element()?, $acc as element()?) as element() {
if (empty($e)) then
$acc
else
local:id(()
, element {node-name($e)} {
$e/@*
, for $node in $e/node()
return typeswitch($node)
case element() return local:id($node, $acc)
default return $node
})
};
The idea is that functions that do more than return their input could be based
on the function, and benefit from tail call optimization.
Kendall
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