I'd like to add a variation on the topics of chapters 5 and 6. Now I
don't have an XPath 3.0 processor around, but I've written and tested
this in another language that has anonymous functions and closures,
and tried to translate it, to the best of my abilities.
The code below illustrates the combination of a closure to create a
recursive function, using Dimitre's two-stage approach to achieve the
recursive call via a previously assigned variable. The instantiation
of the final function is done by function "builder" that preserves the
essential parameters (acting as a closure). Two functions are bullt,
using the definitions of "isZero", "prod" and "sum".
<xsl:variable name = "builder" select = "
function( $term as function(item()*) as item()*,
$op as function(item()*, item()*) as item()*,
$init as item()* ) as function(item()*) as item()*
{ let
$h := function( $x as item()*,
$recurse as function(item()*,function()) ) as item()*
{ if( $term($x) ) then $init
else $op( $x, $recurse( $x - 1, $recurse ) )},
$f := function($x as item()*) as item()*
{ $h( $x, $h ) }
return $f" />
<xsl:variable name = "isZero" select = "
function($x as item()*) as item()*
{$x eq 0}"/>
<xsl:variable name = "prod" select = "
function($x as item()*, $y as item()*) as item()*
{$x*$y}"/>
<xsl:variable name = "sum" select = "
function($x as item()*, $y as item()*) as item()*
{$x + $y}"/>
<xsl:variable name = "faculty" select = "builder($isZero, $prod, 1 )"/>
<xsl:variable name = "series" select = "builder($isZero, $sum, 0 )"/>
-W
On 08/01/2013, Costello, Roger L. <costello(_at_)mitre(_dot_)org> wrote:
Hi Folks,
Dimitre and I collaborated to add a new chapter in the paper, "Pearls of
XSLT and XPath 3.0 Design."
The new chapter describes Dimitre's binary search tree implementation.
Here are the first couple of paragraphs:
CHAPTER 7: BINARY SEARCH TREES
This chapter contains code for creating and processing binary search trees.
The code is implemented entirely in XPath. An advantage of an "XPath-only"
solution is that it can be used (hosted) in many programs--it can be hosted
in XSLT programs, in XQuery programs, and in any other programming language
that hosts XPath. Thus "XPath-only" solutions are highly portable and
reusable.
The XPath code inputs data from an XML document and stores the data into a
binary search tree. By storing the data in a binary tree there are many
operations that can be efficiently performed which would otherwise be
difficult or inefficient.
More ... http://www.xfront.com/Pearls-of-XSLT-and-XPath-3-0-Design.pdf
Dimitre Novatchev and Roger Costello
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