[plt-scheme] undefined value

In the meantime, #f is commonly used when other languages would use
those values below.

Robby

At Sat, 30 Oct 2004 13:50:10 -0400, Matthias Felleisen wrote:
>   For list-related administrative tasks:
>   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> 
> If Scheme's type analysis ever matures enough,
> 
>    (define-struct mtdb ())
> 
> will be your best bet. You get a unique value (make-mtdb) and a 
> matching predicate mtdb?.
> 
> -- Matthias
> 
> 
> 
> On Oct 30, 2004, at 12:33 PM, David J. Neu wrote:
> 
> >   For list-related administrative tasks:
> >   http://list.cs.brown.edu/mailman/listinfo/plt-scheme
> >
> > Hi all,
> >
> > Which would be the appropriate PLT Scheme value to use to represent a
> > NULL value in a database?
> >
> > For example, in Python I'd use None, in C NULL, in Pascal nil.
> >
> > The value will be part of an association list that represents a row in
> > a database, i.e. ((field1 . value1) (field2 . value2) ...) and will be
> > returned from a mzscheme extension.
> >
> > I've been using 'null but that seems wrong.
> >
> > I've been considering scheme_void or scheme_undefined.
> >
> > I'd obviously want to be able to use an existing procedure or write
> > new one to checks if the value of a field is NULL.
> >
> > Many thanks!
> >
> > Cheers,
> > Dave