Re: [xsl] XSLT 2.0 courses?

Subject: Re: [xsl] XSLT 2.0 courses?
From: "Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Mon, 21 Sep 2020 11:01:39 -0000
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 gerrit.imsieke@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> 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.
> Gerrit
> 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
>> Saxonica
>>> 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 $b"? I'm not sure which one will seem more natural to most
>>> Gerrit
>>> On 21.09.2020 10:46, Michael Kay mike@xxxxxxxxxxxx
<mailto:mike@xxxxxxxxxxxx> wrote:
>>>> I've been proposing ($a otherwise $b) to meet this requirement: it
returns $a unless it's an empty sequence, in which case it returns $b.
>>>> For example @price - (@discount otherwise 0)
>>>> It's actually implemented in Saxon 10 if you switch syntax extensions
>>>> Michael Kay
>>>> Saxonica
>>>>> On 21 Sep 2020, at 02:34, Pieter Lamers pieter.lamers@xxxxxxxxxxxx
<mailto:pieter.lamers@xxxxxxxxxxxx> <mailto:pieter.lamers@xxxxxxxxxxxx
<mailto:pieter.lamers@xxxxxxxxxxxx>> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx
<mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>>> wrote:
>>>>> Hi,
>>>>> An avid user of ($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, $b)[1] will return just the first item in the sequence,
'one', and not 'one','two','three', which might be what you want to achieve in
this quasi shorthanded /if/else /construction.
>>>>> Not that you wouldn't know, Liam, just as a heads up to some others in
this audience who might not.
>>>>> Best,
>>>>> Pieter
>>>>> On 19/09/2020 01:54, Liam R. E. Quin liam@xxxxxxxxxxxxxxxx
<mailto:liam@xxxxxxxxxxxxxxxx> wrote:
>>>>>> On Fri, 2020-09-18 at 19:31 +0000, Wendell Piezwapiez@xxxxxxxxxxxxxxx
>>>>>> wrote:
>>>>>>> Hi,
>>>>>>> In addition to Liam's list I think there are a couple more vital
>>>>>>> features
>>>>>>> one needs to get a taste of in XSLT 2.0 or XSLT 3.0, if one has been
>>>>>>> subsisting on an XSLT 1.0 diet:
>>>>>>> * <xsl:for-each-group> and its uses
>>>>>>> * temporary trees -
>>>>>>> * regex support in functions and xsl:analyze-string
>>>>>>> * tunnel parameters?
>>>>>> Yeah, those are all huge, although i think easier to learn than things
>>>>>> like ($a, 'none')[1], which are startling because XSLT 1 didn't have
>>>>>> sequences.
>>>>>> 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
>>>>>> 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
>>>>>> possible.
>>>>>> Liam

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