Re: Prolog type overloading

Hi!
I'd like some type checking into the prolog standard...
In fact I wrote a simply script based on term_extension/3 predicate to
handle that issue.
On the other hand you can just do type checking into the clause body, as:

next(P) :-
\+ is_list(P),
next([S]),
member(P, [S]).

Regards,
/\/\


"George" <me@xxxxxx> ha scritto nel messaggio
news:Pine.GSO.4.58.0606281101110.8172@xxxxxxxxxxxxxxxxxxxxxx
Dear All,

I am wondering whether it is possible to define one predicate in Prolog
that takes two different data types as parameters, but has the same number
of arguments.

As an example, I have a predicate that tells me who is to play next in a
game. If I have in my database next([john,peter]), it means that john and
peter are next to make a move.

I would like to define a predicate with the same name (next) but with the
following logic: if next succeeds with a list, check whether the player I
pass as an argument is member of that list. I wrote it as:

next(P):-
next([S]),
member(P,[S]).

However, this results in infinite looping. Is there a better of doing it
or telling Prolog not to invoke next without a list as the parameter?

Thanks,
George

Computers are useless. They can only give you answers.
Pablo Picasso (1881-1973)



.

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