Subject: Re: [xsl] XPath 3.0: Is it possible to do recursion in an anonymous function? From: Dimitre Novatchev <dnovatchev@xxxxxxxxx> Date: Sun, 14 Oct 2012 10:32:02 -0700 |
> Using Dimitre's technique, I implemented the "until" function: > > <?xml version="1.0" encoding="UTF-8"?> > <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" > xmlns:xs="http://www.w3.org/2001/XMLSchema" > version="3.0"> > > <xsl:output method="text"/> > > <xsl:variable name="isNegative" select="function($x as xs:integer) {$x lt 0}" /> > <xsl:variable name="decrement" select="function($x as xs:integer) {$x - 1}" /> > <xsl:variable name="_until" select=" > function( > $p as function(item()*) as xs:boolean, > $f as function(item()*) as item()*, > $x as item()*, > $_until as function(function(), function(), item()*, function()) as item()* > ) as item()* > {if ($p($x)) then $x else $_until($p, $f, $f($x), $_until)} > " /> > > <xsl:variable name="until" select=" > function( > $p as function(item()*) as xs:boolean, > $f as function(item()*) as item()*, > $x as item()* > ) as item()* > {$_until($p, $f, $x, $_until)} > " /> > > <xsl:template match="/"> > <xsl:value-of select="$until($isNegative, $decrement, 3)" /> > </xsl:template> > > </xsl:stylesheet> > > /Roger > > Nice, Roger, The naming of the last argument makes the code *look* like ordinary recursion. And this could deceive some people! :) Also, the name of this argument will have to change for a new function to match the function name. I would personally prefer a more standard and unchangeable name, such as "_step". To go further, the type of the "_step" argument could be specified as function()+ . This could be used to implement "non-deterministic" functions, where at each step, the next processing step is randomly determined from the available choices ($_step functions). I feel overwhelmed at what can be accomplished with pure XPath 3.0 anonymous functions. -- Cheers, Dimitre Novatchev --------------------------------------- Truly great madness cannot be achieved without significant intelligence. --------------------------------------- To invent, you need a good imagination and a pile of junk ------------------------------------- Never fight an inanimate object ------------------------------------- To avoid situations in which you might make mistakes may be the biggest mistake of all ------------------------------------ Quality means doing it right when no one is looking. ------------------------------------- You've achieved success in your field when you don't know whether what you're doing is work or play ------------------------------------- Facts do not cease to exist because they are ignored. ------------------------------------- Typing monkeys will write all Shakespeare's works in 200yrs.Will they write all patents, too? :) ------------------------------------- I finally figured out the only reason to be alive is to enjoy it.
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