0-arity compound terms (was: Ann: SWI-Prolog 7.1.0)

On 26/11/13 14:19, Jan Wielemaker wrote:
> I agree with Jeff here.  I dislike functor(42, 42, 0) or 42 =.. [42],
> but `fixing' them in favour of something that is heavily doubted and
> certainly still has to prove its value is IMHO a bridge too far.
> As it is now, especially with Jeff's domain error on functor(a(),_,_),
> they can peacefully coexists.   If you don't like it, simply don't use
> it and nothing breaks.

I always used to think of atoms as special cases of compound terms:
0-arity ones.

What is the *motivation* for making a distinction here (did I miss it)?

Kilian