Hello,
nearly completely ignorant on how the internals of any Prolog system
work and maybe a very stupid point, but if not asked (and explained)
somewhere, I'll never understand:
I wonder if there were the possibility to make the following
expressions possible (referring Ulrich's posting on Lambda-like
continuations), and what the reasons for the potential impossibility
(or drawbacks, if possible at all) are:
(i) Ulrich's code:
:- meta_predicate ^(?,0,?).
:- meta_predicate ^(?,1,?,?).
:- meta_predicate ^(?,2,?,?,?).
:- meta_predicate ^(?,3,?,?,?,?).
changed to:
meta_meta_predicate(P) :-
P =.. [^, ?, I, ? | L],
length(L, I),
:- meta_predicate P.
(ii) Ulrich's code again:
^(V1, Goal, V1) :- call(Goal).
^(V1, Goal, V1, V2) :- call(Goal, V2).
^(V1, Goal, V1, V2, V3) :- call(Goal, V2, V3).
^(V1, Goal, V1, V2, V3, V4) :- call(Goal, V2, V3, V4).
^(V1, Goal, V1, V2, V3, V4, V5) :- call(Goal, V2, V3, V4, V5).
changed to:
meta_call(P) :-
P =.. [^, V1, Goal, V1 | L],
CallGoal =.. [Goal | L],
call(CallGoal).
and so on.
IMHO both would need changes in the compiler and I can't see the
consequences (compile time, runtime and semantics), but OTOH, wouldn't
it make handling variable number of arguments possible (there has
already been a discussion on "call/N - how much?"), what otherwise is
only possible using lists as arguments?
Compatibility is another point, of course.
Cheers,
Eckard
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