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self_messages

This simple programming example illustrates the semantics of messages to self (using the (::)/1 control construct), i.e. to the object that received the message being processed.

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

Start by loading the example:

logtalk_load(self_messages(loader)).

The predicate get_local/1 calls the local/1 predicate in self, i.e. in the object that receives the get_local/1 message:

parent::get_local(Local).

prototype::get_local(Local).

The get_default/1 predicate also calls the default/1 predicate in self but predicate is only defined in the parent object; its definition is therefore inherited by the prototype object:

parent::get_default(Default).

prototype::get_default(Local).

The get_undefined/1 predicate also calls the undefined/1 predicate in self but the predicate is only declared and not defined in either object making the messages fail as per closed world assumption:

parent::get_undefined(_).

prototype::get_undefined(_).