Re: [xsl] XSLT 2.0 courses?

Subject: Re: [xsl] XSLT 2.0 courses?
From: "Imsieke, Gerrit, le-tex gerrit.imsieke@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 21 Sep 2020 10:58:29 -0000
Thank you, this is convincing.

One might consider naming the 'otherwise' operator 'alternatively', but this is not the hill I'm going to die on.


On 21.09.2020 12:53, Michael Kay mike@xxxxxxxxxxxx wrote:
Well, I thought about using EBV, so it means (if ($a) then $a else $b), but zero is falsey, so you get surprises with, for example

@price * (1 + (@VAT_Rate otherwise 0.2))

which potentially gives the wrong answer if @VAT_Rate is present but zero. And it also gets complicated with atomization: if the attribute is present but set to a zero length string, which way do you go?

Michael Kay

On 21 Sep 2020, at 11:21, Imsieke, Gerrit, le-tex gerrit.imsieke@xxxxxxxxx <mailto:gerrit.imsieke@xxxxxxxxx> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>> wrote:

If the boolean variable $a is false() instead of an empty sequence,

$a otherwise $b

will return false(). This is the specified behaviour, but I find it a bit counterintuitive. I have a slight preference for the otherwise operator to return $b if $a is false().

Have you thought about defining the otherwise operator as "it returns $a unless it's an empty sequence or a boolean value equal to false(), in which case it returns $b"? I'm not sure which one will seem more natural to most users.


On 21.09.2020 10:46, Michael Kay mike@xxxxxxxxxxxx <mailto:mike@xxxxxxxxxxxx> wrote:
I've been proposing ($a otherwise $b) to meet this requirement: it returns $a unless it's an empty sequence, in which case it returns $b.
For example @price - (@discount otherwise 0)
It's actually implemented in Saxon 10 if you switch syntax extensions on.
Michael Kay
On 21 Sep 2020, at 02:34, Pieter Lamers pieter.lamers@xxxxxxxxxxxx <mailto:pieter.lamers@xxxxxxxxxxxx> <mailto:pieter.lamers@xxxxxxxxxxxx <mailto:pieter.lamers@xxxxxxxxxxxx>> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>>> wrote:


An avid user of ($a, $b)[1] myself, which winks at TransactSQL ISNULL($a, $b) and MySQL IFNULL($a, $b), I do have to remind myself that $a has to be a single item for the /if/else /shortcut to work.

So, in

let $a := ('one','two','three')
let $b := ('none')

return ($a, $b)[1] will return just the first item in the sequence, 'one', and not 'one','two','three', which might be what you want to achieve in this quasi shorthanded /if/else /construction.

Not that you wouldn't know, Liam, just as a heads up to some others in this audience who might not.


On 19/09/2020 01:54, Liam R. E. Quin liam@xxxxxxxxxxxxxxxx <mailto:liam@xxxxxxxxxxxxxxxx> wrote:
On Fri, 2020-09-18 at 19:31 +0000, Wendell Piezwapiez@xxxxxxxxxxxxxxx <mailto:Piezwapiez@xxxxxxxxxxxxxxx>

In addition to Liam's list I think there are a couple more vital
one needs to get a taste of in XSLT 2.0 or XSLT 3.0, if one has been
subsisting on an XSLT 1.0 diet:

* <xsl:for-each-group> and its uses
* temporary trees -
* regex support in functions and xsl:analyze-string
* tunnel parameters?
Yeah, those are all huge, although i think easier to learn than things
like ($a, 'none')[1], which are startling because XSLT 1 didn't have

For those wondering, ($a, $b, $c, ...)[1] returns the first non-empty
non-false item out of $a, $b and $c, so it's a shortcut for
B B B B <xsl:sequence select="if ($a) then $a else $b" />

On regular expressions - it's huge, but it's also dangerous, as e.g. replace(price div 100, '\.\d*$', '') is not a good way to write math:floor().

An XSLT-3-from-scratch course could easily take a full week and be
woefully incomplete. Or totally overwhelming. Or both.

On the other hand, i try & include "don't be afraid of the specs" in
the courses i teach, and then not cover every detail. So maybe it's


Current Thread