Welcome to SWI-Prolog (Multi-threaded, 64 bits, Version 6.6.4)
Copyright (c) 1990-2013 University of Amsterdam, VU Amsterdam
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.

For help, use ?- help(Topic). or ?- apropos(Word).

?- consult('prolang.pl').
% prolang.pl compiled 0.00 sec, 10 clauses
true.

?- listing.

language(smalltalk).
language(lisp).
language(prolog).

:- thread_local thread_message_hook/3.
:- dynamic thread_message_hook/3.
:- volatile thread_message_hook/3.


essence(smalltalk, objects, 'message passing').
essence(lisp, lists, 'recursive functions').
essence(prolog, relations, 'logical inferencing').

history(smalltalk, inventor('Alan Kay'), date(1980)).
history(lisp, inventor('John McCarthy'), date(1959)).
history(prolog, inventor('Alan Comeraur'), date(1971)).
true.

?- halt.