root/trunk/examples/logic/SCRIPT.txt

================================================================
Logtalk - Open source object-oriented logic programming language
Release 2.35.0

Copyright (c) 1998-2009 Paulo Moura.        All Rights Reserved.
Logtalk is free software.  You can redistribute it and/or modify
it under the terms of the "Artistic License 2.0" as published by 
The Perl Foundation. Consult the "LICENSE.txt" file for details.
================================================================


% start by loading the example:

| ?- logtalk_load(logic(loader)).
...


% translate a single logic proposition:

| ?- translator::translate((p v ~q) => (r & k), Cs).
r :- p.
k :- p.
q; r :- .
q; k :- .


Cs = [cl([r],[p]),cl([k],[p]),cl([q,r],[]),cl([q,k],[])]
yes


% translate a single logic proposition printing each translation step:

| ?- translator::step_by_step((p v ~q) => (r & k), Cs).

Processing proposition: p v ~q=>r&k

  1. Remove implications: ~ (p v ~q) v r&k
  2. Distribute negation: ~p&q v r&k
  3. Remove existential quantifiers: ~p&q v r&k
  4. Convert to prenex normal form: ~p&q v r&k
  5. Remove universal quantifiers: ~p&q v r&k
  6. Convert to conjunctive normal form: (~p v r)&(~p v k)&((q v r)&(q v k))
  7. Convert to clauses: [cl([r],[p]),cl([k],[p]),cl([q,r],[]),cl([q,k],[])]

Clauses in Prolog-like notation:
r :- p.
k :- p.
q; r :- .
q; k :- .


Cs = [cl([r],[p]),cl([k],[p]),cl([q,r],[]),cl([q,k],[])]
yes


% translate a single logic proposition printing each translation step:

| ?- translator::step_by_step(all(X, exists(Y, p(X) v ~q(X) => r(X, Y))), Cs).

Processing proposition: all(X, exists(Y, p(X)v~q(X)=>r(X, Y)))

  1. Remove implications: all(X, exists(Y, ~ (p(X)v~q(X))v r(X, Y)))
  2. Distribute negation: all(X, exists(Y, ~p(X)&q(X)v r(X, Y)))
  3. Remove existential quantifiers: all(X, ~p(X)&q(X)v r(X, f1(X)))
  4. Convert to prenex normal form: all(X, ~p(X)&q(X)v r(X, f1(X)))
  5. Remove universal quantifiers: ~p(X)&q(X)v r(X, f1(X))
  6. Convert to conjunctive normal form: (~p(X)v r(X, f1(X)))& (q(X)v r(X, f1(X)))
  7. Convert to clauses: [cl([r(X, f1(X))], [p(X)]), cl([q(X), r(X, f1(X))], [])]

Clauses in Prolog-like notation:
r(X, f1(X)) :- p(X).
q(X); r(X, f1(X)) :- .


X = X
Y = f1(X)
Cs = [cl([r(X, f1(X))], [p(X)]), cl([q(X), r(X, f1(X))], [])] 
yes


% translate a single logic proposition printing each translation step:

| ?- translator::step_by_step(all(X, men(X)  => mortal(X)), Cs).

Processing proposition: all(X, men(X)=>mortal(X))

  1. Remove implications: all(X, ~men(X)v mortal(X))
  2. Distribute negation: all(X, ~men(X)v mortal(X))
  3. Remove existential quantifiers: all(X, ~men(X)v mortal(X))
  4. Convert to prenex normal form: all(X, ~men(X)v mortal(X))
  5. Remove universal quantifiers: ~men(X)v mortal(X)
  6. Convert to conjunctive normal form: ~men(X)v mortal(X)
  7. Convert to clauses: [cl([mortal(X)], [men(X)])]

Clauses in Prolog-like notation:
mortal(X) :- men(X).


X = X
Cs = [cl([mortal(X)], [men(X)])] 
yes