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\f0\fs22 \cf2 \CocoaLigature0 Last login: Wed Sep  4 10:43:27 on ttys000\
mba:Prolog johnz$ ls\
proglang.pro		proglang.pro~		proglangdemo1.txt\
mba:Prolog johnz$ swipl\
Welcome to SWI-Prolog (threaded, 64 bits, version 8.0.3)\
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software.\
Please run ?- license. for legal details.\
\
For online help and background, visit http://www.swi-prolog.org\
For built-in help, use ?- help(Topic). or ?- apropos(Word).\
\
?- consult('proglang.pro').\

\f1\b true.
\f0\b0 \
\
?- listing.\
\
language(smalltalk).\
language(lisp).\
language(prolog).\
\
:- multifile prolog_predicate_name/2.\
\
\
:- multifile prolog_clause_name/2.\
\
\
history(smalltalk, inventor('Alan Kay'), date(1980)).\
history(lisp, inventor('John McCarthy'), date(1959)).\
history(prolog, inventor('Alan Colmeraur'), date(1971)).\
\
:- dynamic prolog_exception_hook/4.\
:- multifile prolog_exception_hook/4.\
\
prolog_exception_hook(error(E, context(Ctx0, Msg)), error(E, context(prolog_stack(Stack), Msg)), Fr, GuardSpec) :-\
    prolog_stack:\
    (   current_prolog_flag(backtrace, true),\
        \\+ is_stack(Ctx0, _Frames),\
        (   atom(GuardSpec)\
        ->  debug(backtrace,\
                  'Got uncaught (guard = ~q) exception ~p (Ctx0=~p)',\
                  [GuardSpec, E, Ctx0]),\
            stack_guard(GuardSpec),\
            Guard=GuardSpec\
        ;   prolog_frame_attribute(GuardSpec,\
                                   predicate_indicator,\
                                   Guard),\
            debug(backtrace,\
                  'Got exception ~p (Ctx0=~p, Catcher=~p)',\
                  [E, Ctx0, Guard]),\
            stack_guard(Guard)\
        ),\
        (   current_prolog_flag(backtrace_depth, Depth)\
        ->  Depth>0\
        ;   Depth=20\
        ),\
        get_prolog_backtrace(Depth,\
                             Stack0,\
                             [frame(Fr), guard(Guard)]),\
        debug(backtrace, 'Stack = ~p', [Stack0]),\
        clean_stack(Stack0, Stack1),\
        join_stacks(Ctx0, Stack1, Stack)\
    ).\
\
essence(smalltalk, objects, 'message passing').\
essence(lisp, lists, 'recursive functions').\
essence(prolog, relations, 'logical inferencing').\
\
:- thread_local thread_message_hook/3.\
:- dynamic thread_message_hook/3.\
:- volatile thread_message_hook/3.\
\

\f1\b true.
\f0\b0 \
\
?- halt.\
mba:Prolog johnz$ }