Re: [xsl] XSLT 2.0 courses?

["Imsieke, Gerrit, le-tex gerrit.imsieke@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

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.

Gerrit

On 21.09.2020 10:46, Michael Kay 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 $b.
>
> For example @price - (@discount otherwise 0)
>
> It's actually implemented in Saxon 10 if you switch syntax extensions on.
>
> Michael Kay
> Saxonica
>
> > On 21 Sep 2020, at 02:34, Pieter Lamers pieter.lamers@xxxxxxxxxxxx 
> > <mailto:pieter.lamers@xxxxxxxxxxxx> 
> > <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx 
> > <mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>> wrote:
> >
> > Hi,
> >
> > An avid user of ($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, $b)[1] will return just the first item in the sequence, 
> > 'one', and not 'one','two','three', which might be what you want to 
> > achieve in this quasi shorthanded /if/else /construction.
> >
> > Not that you wouldn't know, Liam, just as a heads up to some others in 
> > this audience who might not.
> >
> > Best,
> > Pieter
> >
> > On 19/09/2020 01:54, Liam R. E. Quin liam@xxxxxxxxxxxxxxxx wrote:
> > > On Fri, 2020-09-18 at 19:31 +0000, Wendell Piezwapiez@xxxxxxxxxxxxxxx
> > > wrote:
> > > > Hi,
> > > >
> > > > In addition to Liam's list I think there are a couple more vital
> > > > features
> > > > one needs to get a taste of in XSLT 2.0 or XSLT 3.0, if one has been
> > > > subsisting on an XSLT 1.0 diet:
> > > >
> > > > * <xsl:for-each-group> and its uses
> > > > * temporary trees -
> > > > * regex support in functions and xsl:analyze-string
> > > > * tunnel parameters?
> > > Yeah, those are all huge, although i think easier to learn than things
> > > like ($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