Re: Ann: SWI-Prolog 7.1.0

On 11/27/2013 06:25 AM, Richard A. O'Keefe wrote:
> No, the special role does NOT depend on whether or not there
> are additional arguments.  The first element of the list is
> ALWAYS the function symbol and the number of remaining elements
> is ALWAYS the arity and X =.. [X] for EVERY term X that is neither
> a variable nor a compound term.

You are just moving the additional tests elsewhere: into functor/3.
I agree that =../2 and functor/3 are designed to form a good combo.
I'll quote your "Univ is admittedly a relic of the pre-Cambrian.".
Joining these two conclusion, I think we should conclude that
functor/3 is also a relic.

Changing these relics breaks too much (I tried).  That is why
I've defined a new pair of predicates.  I assume they will
just co-exist.  In theory, it should be possible that at some
point we deprecate functor/3 and =../2.

	Cheers --- Jan

> The only thing that is special is that numbers cannot be the
> function symbols of compound terms, but that has nothing to do
> with univ.  You can implement the traditional univ as
>
> 	=..(Term, [Function|Arguments]) :-
> 	    (   nonvar(Term) ->
> 		functor(Term, Function, Arity),
> 		length(Arguments, Arity)
> 	    ;   length(Arguments, Arity),
> 	        functor(Term, Function, Arity)
> 	    ),
> 	    '=.. arguments'(Arguments, 0, Term).
>
> 	'=.. arguments'([], _, _).
> 	'=.. arguments'([Arg|Args], N0, Term) :-
> 	    N1 is N0 + 1,
> 	    arg(N1, Term, Arg),
> 	    '=.. arguments'(Args, N1, Term).