Dear Wouter,
There is one more important difference on the syntactic level.
With the arrow operator, the left-hand-side is implicitly bound to the first
parameter of the function.
@address => replace(@postcode, "", "q")
is the same as
replace(@address, @postcode, "", "q")
With the simple map operator, the context item must be explicitly referred to,
like so:
@address ! replace(., @postcode, "", "q")
What may create confusion is that some functions have several signatures, some
of which implicitly refer to the context item. But this is a very different
mechanism.
For example :
@address ! string(.) (: explicitly passed context item :)
@address ! string() (: context item passed implicitly to string#0, which is
context-dependent)
@address => string() (: context item passed implicitly to string#1 via the =>
operator, but string#1 is context-independent)
I hope I got it right!
Kind regards,
Ghislain
> On 2 Aug 2017, at 11:27, W.S. Hager <wsha...@gmail.com> wrote:
>
> Hi Michael,
>
> The way you used the arrow operator in the example would be the way I
> expected it to work, namely by explicitly addressing the context, but it
> seems that it doesn't. It's actually implicitly binding the first argument of
> the function on the right to the value on the left. Or is there an exception
> I don't know about?
>
> Thanks.
>
> Op 1 aug. 2017 18:58 schreef "Michael Kay" <m...@saxonica.com>:
> In the case of singletons there's very little difference, but (as I now see
> Christian has pointed out), with sequences the effect is quite different.
>
> Also, of course, "!" changes the context item, so
>
> @address => replace(@postcode, "", "q") works, while
>
> @address ! replace(@postcode, "", "q") doesn't.
>
> Michael Kay
> Saxonica
>
> > On 1 Aug 2017, at 13:27, W.S. Hager <wsha...@gmail.com> wrote:
> >
> > Hi,
> >
> > Is there any advantage to using the 3.1 arrow operator over the simple map
> > operator?
> >
> > $string => upper-case() => normalize-unicode() => tokenize("\s+")
> >
> > versus
> >
> > $string ! upper-case(.) ! normalize-unicode(.) ! tokenize(.,"\s+")
> >
> > Thanks,
> > Wouter
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>
>
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