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Re: [xsl] XSLT 2.0 courses?

2020-09-21 06:01:44
Perhaps we should call it "bzw" - a German word that is sadly missing from 


On 21 Sep 2020, at 11:58, Imsieke, Gerrit, le-tex 
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:

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(_at_)saxonica(_dot_)com 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 
<mailto:xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com>> 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 


On 21.09.2020 10:46, Michael Kay mike(_at_)saxonica(_dot_)com 
<mailto:mike(_at_)saxonica(_dot_)com> 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 
<mailto:xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com>>> 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(_at_)fromoldbooks(_dot_)org 
<mailto:liam(_at_)fromoldbooks(_dot_)org> wrote:
On Fri, 2020-09-18 at 19:31 +0000, Wendell 

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 $c, so it's a shortcut for
    <xsl:sequence select="if ($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

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


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