Re: How to write (existential) predicates with maps/Wh

> When I started this I was fairly neutral about it, but I've now used
Javascript enough to form a strong distaste for weak typing.

What about Typescript?

Cheers,
Dimitre Novatchev

On Tue, Feb 12, 2019 at 8:41 AM Michael Kay mike@xxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> I've improved the error message so it now says:
>
> FORG0006: Effective boolean value is not defined for sequence starting with
a map
>   (map{"name":"foo", })
>
> The reason for the problem:
>
> > parse-json($json)?locations?*[?types?*[?name = 'foo']]"
>
> locations?* => a sequence of maps
>
> ?types => a sequence of arrays
>
> ?types?* => a sequence of maps
>
> So the value of the outer predicate is a sequence of zero-or-more maps, and
you can't get the EBV of a map.
>
> Created W3C test case predicate-056.
>
> >What is the reason that the effective boolean value was not extended to
give true for a sequence with a map?
>
> Sentiment in the WGs slowly moved away from weak typing and implicit
conversion over the years that followed XPath 1.0 (Getting arrays to be
atomizable was a bit of a battle). I think the richer the type system becomes,
the more useful it is to have errors rather than implicit conversions. I saw a
horrible one last week in which someone did <xsl:with-param>2</xsl:with-param>
and then tried to use the value as a "numeric" predicate, not realising it was
actually a node.
>
> When I started this I was fairly neutral about it, but I've now used
Javascript enough to form a strong distaste for weak typing.
>
> Michael Kay
> Saxonica
>
>
>
> > On 12 Feb 2019, at 16:07, Martin Honnen martin.honnen@xxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > On 12.02.2019 15:40, Michael Kay mike@xxxxxxxxxxxx wrote:
> >> I'm having trouble understanding/reproducing this. Can you supply a
complete repro? (I.e., the source data that results in this error)
> >
> >
> > The example JSON is e.g.
> >
> > {
> >    "locations" : [
> >      {
> >          "id" : "i1",
> >          "types" : [
> >              {
> >                "name" : "foo"
> >              },
> >              {
> >                "name" : "bar"
> >              }
> >          ]
> >      },
> >      {
> >          "id" : "i2",
> >          "types" : [
> >              {
> >                "name" : "baz"
> >              }
> >          ]
> >      },
> >      {
> >          "id" : "i3",
> >          "types" : [
> >              {
> >                "name" : "foo"
> >              },
> >              {
> >                "name" : "baz"
> >              }
> >          ]
> >      }
> >    ]
> > }
> >
> > If you pass it to the parse-json function and use the result as the
context item to the three XPath expressions I have posted then the first one
gives that error while the other two return two maps.
> >
> > A complete repro in XSLT is
> >
> > <?xml version="1.0" encoding="UTF-8"?>
> > <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
> >       xmlns:xs="http://www.w3.org/2001/XMLSchema"
> >       exclude-result-prefixes="#all"
> >       version="3.0">
> >
> >  <xsl:output method="adaptive"/>
> >
> >  <xsl:param name="json" as="xs:string">
> > {
> >    "locations" : [
> >      {
> >          "id" : "i1",
> >          "types" : [
> >              {
> >                "name" : "foo"
> >              },
> >              {
> >                "name" : "bar"
> >              }
> >          ]
> >      },
> >      {
> >          "id" : "i2",
> >          "types" : [
> >              {
> >                "name" : "baz"
> >              }
> >          ]
> >      },
> >      {
> >          "id" : "i3",
> >          "types" : [
> >              {
> >                "name" : "foo"
> >              },
> >              {
> >                "name" : "baz"
> >              }
> >          ]
> >      }
> >    ]
> > }
> >  </xsl:param>
> >
> >  <xsl:template match="/" name="xsl:initial-template">
> >    <xsl:sequence select="parse-json($json)?locations?*[?types?*[?name =
'foo']]"/>
> >  </xsl:template>
> >
> > </xsl:stylesheet>
> >
> >
> >
> >
> >>> On 11 Feb 2019, at 12:09, Martin Honnen martin.honnen@xxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> >>>
> >>> When using XPath 3.1 (e.g. in XSLT 3) on maps I have found that I have
to change my coding habit a bit when writing predicates that want to check the
existence of some nested map, while I hoped to be able to write e.g.
> >>>
> >>>  ?locations?*[?types?*[?name = 'foo']]
> >>>
> >>> to select all (map) members of the "locations" array that have a "types"
array with at least one (map) member having a property "name" with value "foo"
I get an error
> >>>
> >>> Effective boolean value is not defined for sequence starting with an
atomic value other than a boolean, number, or string
> >>>
> >>>
> >>> So in contrast to my experience with writing predicates on XML it seems
for maps I have to explicitly use the "exists" function e.g.
> >>>
> >>>  ?locations?*[exists(?types?*[?name = 'foo'])]
> >>>
> >>> or a "some .. in" expression
> >>>
> >>>  ?locations?*[some $m in ?types?* satisfies $m?name = 'foo']
> >>>
> >>>
> >>> Is there any more compact way to write such a check?
> >>>
> >>> What is the reason that the effective boolean value was not extended to
give true for a sequence with a map?