[Versa] first class functions

[Uche Ogbuji]

On Mon, 2005-09-26 at 11:14 -0600, Michael Olson wrote:
> On Sep 26, 2005, at 11:09 AM, Jeremy Kloth wrote:
> 
> > On Monday 26 September 2005 11:04 am, Michael Olson wrote:
> >>> I see them being differentiated by bindings alone.  If the qname (in
> >>> expanded
> >>> form) is bound to a function where a function-reference is allowed,
> >>> use it.
> >>> There may be other issues I'm missing, but this doesn't seem  
> >>> difficult
> >>> for an
> >>> implementation to do.
> >>
> >> There is, because "rdf:type(all())" is a valid function call.  We
> >> discussed it on some thread on the list, but basically it translates  
> >> to
> >> a traverse expression of all() - rdf:type -> *.  So, in the case of
> >> rdf:type it is _always_ a bound function call, and it is always a  
> >> valid
> >> qname-constant.
> >>
> >> It would even be valid not in the special case as a function can  
> >> always
> >> be defined with a qname, and can always conflict with a  
> >> qname-constant.
> >>
> >> @function ext:name = all();
> >> list (ext:name)
> >
> > So, you are saying a *function-reference* is a valid input to the list
> > function?
> >
> 
> If a "function-reference" is a first class datatype, then from a  
> grammars point of view it is.  It would return
> 
> [ ext:name ]
> 
> as a results which could then be passed to a different function the  
> expects a list of function references, ie distribute() could  
> conceivably take a list of function references as an argument.

Yes, and I see the problem Mike's illustrating.  However, I still
advocate the opposite disambiguation:

http://lists.fourthought.com/pipermail/versa/2005-September/000221.html

To me, interpretation of a qname resource as a function is more magic
than first-class functions (after all, Versa is intended to have a lot
of the character of a functional language), so I'd rather put the
greater syntax where the greater magic is.


-- 
Uche Ogbuji                               Fourthought, Inc.
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