Logtalk - Hello World

According to the SWI-Prolog Mailing List, ...

Logtalk is an object-oriented logic programming language that can use most
Prolog implementations as a back-end compiler. As a multi-paradigm language, it includes support for both prototypes and classes, protocols (interfaces), component-based programming through category-based composition, event-driven programming, and high-level multi-threading programming.

For this, it seems worth trying Logtalk in order to lift Prolog programming to a different level (more contained). As usually, the first program show-casing some programming language is the famous "hello world" program. Unlike, other programming languages the Prolog version of "hello world" is a family relation.

Since this post is merely to maintain flow, I will present a "hello world" in Logtalk. Logtalk helps decomposing program logic by offering the well known concept of object and interface (including visibility of object members).

Behold .. the magic "hello world":

:- object(first_program).
  :- public(main/1).

  hello_world(Text) :- write(Text), nl.

  main(Text) :-
    hello_world(Text).

:- end_object.

As can be guessed, the program is quite simple. An object called first program is declared,
offering a publicly visible method called main. main passes one argument, i.e. some text to print, to the famous hello_world procedure. hello_world calls Prolog's write function to write the passed text on some line, adding a newline at the end of the text.

After consulting the program, one may call main using

first_program::main('Hello World').