Using call/2 to send messages

[hnbeck]

Hi,

what is not clear to me: I can do things in Prolog like
A = myPredicate, B = myArgument, call(A, B).
I can do in Logtalk
A = myObject B=myMessage, A::B.

if myMessage/0. But what is the way to do it if myMessage requires Arguments (myMessage/N, N>0)?

Cheers

Hans

[pmoura]

Isn't doing the following practical in your case:

..., Message =.. [Name| Arguments], Object::Message, ...

In alternative, if the goal is called from inside an object (or category), you can simply do:

..., call(Object::Name, Arg1, ...), ...

In Logtalk, call/N are interpreted as private meta-predicates and thus cannot be used as messages. The main reason for the private scope is that meta-arguments are always called in the context of the sender. Thus, a Object::call(Name, Arg1, ...) goal would imply calling Name(Arg1, ...) in sender and not being interpreted as a message to the object.

[hnbeck]

Hi Paulo,

argh, yes of course :). That's perfect, I forgot this possibility. Sorry for the trivial question :)

Cheers

Hans

[pmoura]

Not really trivial as far as call/N handling of closures is concerned. Outside an object (or category), call/N is Prolog call/N and thus doesn't handle properly closures that use Logtalk control constructs such as, for example, ::/1, ::/2, or ^^/1. But inside an object (or category), call/N is handled by the Logtalk compiler/runtime and is thus aware of all Logtalk control constructs. Then there's also the difference between Prolog and Logtalk meta-predicate semantics. While in Logtalk meta-arguments are always called in the calling context, in Prolog meta-arguments are called in either the calling context or in the meta-predicate definition context depending if the call is, respectively, implicitly or explicitly module-qualified.