Subject: Re: [xsl] XPath 3.0: Is it possible to do recursion in an anonymous function? From: Michael Kay <mike@xxxxxxxxxxxx> Date: Sun, 14 Oct 2012 09:03:46 +0100 |
Michael Kay Saxonica
Finally, it is possible to hide the use of the second argument -- like this:
<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs"> <xsl:output method="text"/>
<xsl:template match="/"> <xsl:sequence select= "let $f := function($n as xs:integer, $f1 as function(xs:integer, function()) as xs:integer ) as xs:integer {if($n eq 0) then 1 else $n * $f1($n -1, $f1) }, $F := function($n as xs:integer) as xs:integer {$f($n, $f)} return $F(5) "/> </xsl:template> </xsl:stylesheet>
Cheers, Dimitre
On Sat, Oct 13, 2012 at 12:51 PM, Dimitre Novatchev <dnovatchev@xxxxxxxxx> wrote:Boh my previous answers had a slight issue (that didn't prevent Saxon from executing them and producing the correct result) with the typing of the "mock" function parameter $f1.
Here is this corrected:
<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs"> <xsl:output method="text"/>
<xsl:template match="/"> <xsl:sequence select= "let $f := function($n as xs:integer, $f1 as function(xs:integer, function()) as xs:integer ) as xs:integer {if($n eq 0) then 1 else $n * $f1($n -1, $f1) } return $f(5, $f) "/> </xsl:template> </xsl:stylesheet>
Cheers, Dimitre
On Sat, Oct 13, 2012 at 12:47 PM, Dimitre Novatchev <dnovatchev@xxxxxxxxx> wrote:Here is an equivalent XSLT-based solution -- i both cases there is no literal function defined -- just an inline one:
<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-result-prefixes="xs"> <xsl:output method="text"/>
<xsl:template match="/"> <xsl:sequence select= "let $f := function($n as xs:integer, $f1 as function(xs:integer) as xs:integer ) as xs:integer {if($n eq 0) then 1 else $n * $f1($n -1, $f1) } return $f(5, $f) "/> </xsl:template> </xsl:stylesheet>
Again, the correct result is produced:
120
Cheers, Dimitre
On Sat, Oct 13, 2012 at 12:37 PM, Dimitre Novatchev <dnovatchev@xxxxxxxxx> wrote:You are right, but there is an easy workaround.
Here is an example with an in-line factorial function:
declare option saxon:output "omit-xml-declaration=yes"; let $f := function($n as xs:integer, $f1 as function(xs:integer) as xs:integer ) as xs:integer {if($n eq 0) then 1 else $n * $f1($n -1, $f1) } return $f(5, $f)
The result we get is correct:
120
Cheers, Dimitre
On Sat, Oct 13, 2012 at 12:03 PM, Costello, Roger L. <costello@xxxxxxxxx> wrote:Hi Folks,
Is it possible to do recursion in an anonymous function?
Example: I would like to implement an "until" function. It has three arguments:
1. p is a boolean function 2. f is a function on x 3. x is the value being processed
Read the following function call as: decrement 3 until it is negative $until ($isNegative, $decrement, 3)
where $isNegative := function($x as xs:integer) {$x lt 0} $decrement := function($x as xs:integer) {$x - 1}
Here's how I attempted to implement function until:
$until := function( $p as function(item()*) as xs:boolean, $f as function(item()*) as item()*, $x as item()* ) as item()* { if ($p($x)) then $x else $until($p, $f, $f($x)) <-- RECURSE ...THIS IS NOT ALLOWED, I THINK }
Is there a way to implement function until in XPath 3.0? (I know how to implement it in XSLT 3.0)
/Roger
-- 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.
-- 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.
-- 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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