Subject: Re: [xsl] XSLT 2.0 courses? From: "Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Mon, 21 Sep 2020 10:53:19 -0000 |
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 <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 $b"? I'm not sure which one will seem more natural to most users. > > Gerrit > > On 21.09.2020 10:46, Michael Kay mike@xxxxxxxxxxxx wrote: >> I've been proposing ($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
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