Re: [xsl] XSLT repetition constructs

["Dimitre Novatchev dnovatchev@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

On Wed, Mar 6, 2019 at 5:01 AM John Lumley john@xxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:


> > All of these are *mapping" operations, like the map function in
> > Haskell. These have nothing to do with repetition.
>
> Note that the XSLT3.0 specification does actually describe these under a
> chapter heading "Repetition".....
>

Then this is a mistake in the specification -- time for errata.
Repetition implies time passing during the transformation and there is
no notion of "passed time" or time-ordering of execution in XSLT. This
was by design. In fact special care was taken so that functions like
current-time() always return the same value during transformation.

To put it in other words, if we apply templates to a set of items and
output (using <xsl:message/>) the value of current-time() within the
selected template for each item, we get the same value -- so all these
operations were executed at the same time...  This definitely is not
"repetition"

> And one can consider a mapping over a finite set of domain points as
> 'repeat this function over each of these points' ....

"Repeat" means do something first and then do it again. If we do not
specify what is to be done "first" then we cannot speak about
repetition.

It would be correct to say instead: "**Apply** this function on each of these"

Cheers,
Dimitre

>
> On 05/03/2019 22:17, Dimitre Novatchev dnovatchev@xxxxxxxxx wrote:
> > It isn't correct to use "repetition" for a set of operations that are
> > independent from each other and can be executed in any order or in
> > parallel.
> >
> > In this group fall such operations as <xsl:for-each>. the XPath for
> > expression, the ! (bang) operator and applying a function in the last
> > location step of an XPath step-expression (sorry if I don't remember
> > the exact terminology).
> >
> > All of these are *mapping" operations, like the map function in
> > Haskell. These have nothing to do with repetition.
>
> Note that the XSLT3.0 specification does actually describe these under a
> chapter heading "Repetition".....
>
> And one can consider a mapping over a finite set of domain points as
> 'repeat this function over each of these points' ....
>
> --
> *John Lumley* MA PhD CEng FIEE
> john@xxxxxxxxxxxx <mailto:john@xxxxxxxxxxxx>
> on behalf of Saxonica Ltd
> 



-- 
Cheers,
Dimitre Novatchev
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