Re: [xsl] XPath (and other W3C drafts)

Subject: Re: [xsl] XPath (and other W3C drafts)
From: Florent Georges <lists@xxxxxxxxxxxx>
Date: Wed, 16 Dec 2009 15:57:14 +0000 (GMT)
Eliot Kimber wrote:

> At the risk of seeming dim or lazy or both, can someone
> explain the implications of these new features?

  Using 'let', you can bind
a variable directly in XPath.  There
is of course no impact on XQuery.  In
XSLT, that is sometimes
convenient to be able to write a single XPath
expression without
requiring to split it into several expressions or to write
stylesheet function.  And that's important too for other host
Using first-class function items, you can manipulate functions
as items.  For
instance, you can pass a function as parameter to
another function.  Think for
instance about a sorting function,
taking a function item parameter to compare
two items:

      $seq as items()*,
      $comparator as
function($lhs as item(), $rhs as item())

  You can call it like:
sort((2, 1, 3), my:less-than#2)

or even like:

      (2, 1, 3),
function ($lhs as xs:integer, $rhs as xs:integer)
        as xs:boolean
        if ( $ascending ) then $lhs le $rhs else $lhs gt $rhs
That allow one to write higher-order functions (such a function
that takes a
function item as param or return a function item as
result).  I hope that will
boost writing of more general-purpose
libraries for XSLT and XQuery...

that's just what comes directly in mind, others can maybe
give more (and more
precise) use cases.


Florent Georges

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