Re: RfD: more powerful "any" types

On Wed, 2009-09-09 at 07:47 -0400, Alvaro Herrera wrote:
> Peter Eisentraut wrote:
> > On Tue, 2009-09-08 at 10:23 -0700, David E. Wheeler wrote:
> > > On Sep 8, 2009, at 10:15 AM, Tom Lane wrote:
> > > 
> > > >>     arg_a IS DISTINCT FROM arg_b
> > > >
> > > > Surely you'd want arg_a and arg_b constrained to the same type,
> > > > otherwise there is no certainty that that means anything at all.
> > > 
> > > Yes, for the purposes of pgTAP perhaps so. Then it's on the user to do  
> > > the cast, because she decides that the cast is appropriate. Otherwise,  
> > > as I said, perhaps it'd be too magical.
> > 
> > That's beginning to sound a bit like a generics feature.  E.g.,
> > 
> > CREATE FUNCTION the_same<T>(arg_a T, arg_b T) RETURNS bool AS $$
> > SELECT arg_a IS DISTINCT FROM arg_b;
> > $$;
> 
> Well, you can write that one with anyelement already.

Well, so far we've only seen use cases in this thread that either
already work or that are not well-defined. ;-)