Re: Is there a way to implement feedback loops in XProc?

here is another somewhat simpler data point

https://github.com/innovimax/xproc/blob/master/fizzbuzz.xpl

hth, J


On Wed, May 1, 2013 at 10:20 PM, Geert Josten <geert.josten@dayon.nl> wrote:

> Hi Roger,
>
> You can't tie the output of a step to the input of the same step, but you
> can add a step as a child of itself. Just make sure you wrap it in some
> conditional to terminate recursion.
>
> Perhaps not the most lucid example, but you could take a look at
> expand-dirs in
> https://github.com/grtjn/xproc-ebook-conv/blob/master/src/nl/grtjn/xproc/u
> til/utils.xpl. It does a recursive reading of a directory..
>
> Kind regards,
> Geert
>
> > -----Oorspronkelijk bericht-----
> > Van: Costello, Roger L. [mailto:costello@mitre.org]
> > Verzonden: woensdag 1 mei 2013 21:36
> > Aan: xproc-dev@w3.org
> > Onderwerp: Is there a way to implement feedback loops in XProc?
> >
> > Hi Folks,
> >
> > The spec says [1] that no feedback loops are allowed in an XProc
> pipeline:
> >
> >     It is a static error (err:XS0001) if there
> >     are any loops in the connections between
> >     steps: no step can be connected to itself
> >     nor can there be any sequence of connections
> >     through other steps that leads back to itself.
> >
> > So how are recursive structures processed?
> >
> > As a simple example, suppose "Section" is defined recursively:
> >
> > Section = Title | Title Section
> >
> > If XProc supported feedback loops I would create a step in the pipeline
> that
> > processes the content of a Section and the output is the nested Section,
> > which is is fed back around to the step:
> >
> > ---> Step (process Section content) ----------
> > ^                                                                     |
> > |                                     |
> > -------<--------<------------------<-----------<----
> >                   (nested Section)
> >
> > Since feedback loops are not allowed, how is this type of thing
> > accomplished in XProc? Note: I need to implement this using XProc and
> not
> > simply hand it off to XSLT to implement the recursive processing.
> >
> > /Roger
> >
> > [1] http://www.w3.org/XML/XProc/docs/langspec.html#connections
>
>