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yap-6.3/packages/ProbLog/problog/termhandling.yap
2011-06-26 23:13:43 +01:00

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%%% -*- Mode: Prolog; -*-
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% $Date: 2011-04-09 12:00:00 +0200 (Sat, 09 Apr 2011) $
% $Revision: 5890 $
%
% Main authors of this file:
% Bernd Gutmann
%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
:- module(termhandling, [term_element/2,
propagate/5,
propagate_interpretation/3,
simplify/3,
list_to_disjunction/2,
list_to_conjunction/2,
op( 551, yfx, <=> ),
not/2]).
% propagate( +OldTerm, +AtomToReplace, +ReplacementTermForAtom, -NewTerm, -ReplaceHasHappend).
% simplify(+OldTerm,-NewTerm,-SimplificationHasHappend).
% list_to_disjunction(+list,-Disjunction).
% list_to_conjunction(+list,+Conjunction).
:- op( 551, yfx, <=> ).
:- style_check(all).
:- yap_flag(unknown,error).
%========================================================================
%=
%=
%= term_element(+GroundTerm, ?Atom)
%========================================================================
term_element((X,Y),Z) :-
(term_element(X,Z);term_element(Y,Z)).
term_element((X;Y),Z) :-
(term_element(X,Z);term_element(Y,Z)).
term_element((X <=> Y),Z) :-
(term_element(X,Z);term_element(Y,Z)).
term_element(\+ X,Z) :-
term_element(X,Z).
term_element('$atom'(X),'$atom'(X)) :-
X \== true,
X \== false.
% or(+Boolean,+Boolean,-Boolean)
or(true,_,true).
or(false,X,X).
% not(+Boolean,-Boolean)
not(true,false).
not(false,true).
%========================================================================
%=
%=
%= propagate_interpretation(+GroundTerm, +ID, -GroundTerm)
%========================================================================
propagate_interpretation((X,Y),ID,(X2,Y2)) :-
propagate_interpretation(X,ID,X2),
propagate_interpretation(Y,ID,Y2).
propagate_interpretation((X;Y),ID,(X2;Y2)) :-
propagate_interpretation(X,ID,X2),
propagate_interpretation(Y,ID,Y2).
propagate_interpretation((X <=> Y),ID,(X2 <=> Y2)) :-
propagate_interpretation(X,ID,X2),
propagate_interpretation(Y,ID,Y2).
propagate_interpretation((\+ X), ID,\+ X2) :-
propagate_interpretation(X,ID,X2).
propagate_interpretation('$atom'(X),ID,Value) :-
(
user:known(ID,X,Value)
->
true;
Value='$atom'(X)
).
%========================================================================
%=
%=
%=
%========================================================================
propagate((X,Y),A,AValue,(X2,Y2),Result) :-
propagate(X,A,AValue,X2,Result1),
propagate(Y,A,AValue,Y2,Result2),
or(Result1,Result2,Result).
propagate((X;Y),A,AValue,(X2;Y2),Result) :-
propagate(X,A,AValue,X2,Result1),
propagate(Y,A,AValue,Y2,Result2),
or(Result1,Result2,Result).
propagate((X <=> Y),A,AValue,(X2 <=> Y2),Result) :-
propagate(X,A,AValue,X2,Result1),
propagate(Y,A,AValue,Y2,Result2),
or(Result1,Result2,Result).
propagate((\+ X), A, AValue,\+ X2,Result) :-
propagate(X,A,AValue,X2,Result).
propagate('$atom'(X),'$atom'(A),AValue,X2,Result) :-
(
X==A
->
(
X2=AValue,
Result=true
);
(
X2=X,
Result=false
)
).
propagate(true,_,_,true,false).
propagate(false,_,_,false,false).
%========================================================================
%=
%=
%=
%========================================================================
negate_atom(\+ '$atom'(X), '$atom'(X)).
negate_atom( '$atom'(X),\+ '$atom'(X)).
occurs_check_and((X,_), A) :-
occurs_check_and(X,A),
!.
occurs_check_and((_,Y), A) :-
occurs_check_and(Y,A).
occurs_check_and( '$atom'(X), '$atom'(X)).
occurs_check_or((X;_), A) :-
occurs_check_or(X,A),
!.
occurs_check_or((_;Y), A) :-
occurs_check_and(Y,A).
occurs_check_or( '$atom'(X), '$atom'(X) ).
%========================================================================
%=
%= Tries to simplify Term. If succeeded Status=true and SimplifiedTerm
%= is bound to the simplified term. If not succeeded Status=false and
%= SimplifiedTerm=Term.
%=
%= Only works for ground terms! If non-ground terms are used, the
%= the result is undefined!!!
%=
%= simplify(+Term, -SimplifiedTerm, -Status)
%=
%========================================================================
simplify(Term,Term3,true) :-
simplify_intern(Term,Term2,Result),
Result==true,
!,
simplify(Term2,Term3,_).
simplify(Term,Term,false).
%-----------
simplify_intern( (X<=>Y), NewTerm, Result) :-
simplify_intern_implication(X,Y,NewTerm,Result).
simplify_intern((\+ X), NewTerm,Result) :-
simplify_intern_negation(X,NewTerm,Result).
simplify_intern( (X;Y), NewTerm, Result) :-
simplify_intern_or(X,Y,NewTerm,Result).
simplify_intern( (X,Y), NewTerm, Result) :-
simplify_intern_and(X,Y,NewTerm,Result).
simplify_intern('$atom'(X),'$atom'(X),false).
simplify_intern(true,true,false).
simplify_intern(false,false,false).
%-----------
simplify_intern_or( true,_,true,true) :-
!.
simplify_intern_or( false,X,X,true) :-
!.
simplify_intern_or(_,true,true,true) :-
!.
simplify_intern_or(X,false,X,true) :-
!.
% quite expensive
% simplify_intern_or(X,Y,true,true) :-
% negate_atom(X,X2),
% occurs_check_or(Y,X2),
% !.
simplify_intern_or(X,Y,(X2;Y2),Result) :-
!,
simplify_intern(X,X2,Result1),
simplify_intern(Y,Y2,Result2),
or(Result1,Result2,Result).
%-----------
simplify_intern_and( true,X,X,true) :-
!.
simplify_intern_and( false,_,false,true) :-
!.
simplify_intern_and(X,true,X,true) :-
!.
simplify_intern_and(_,false,false,true) :-
!.
% quite expensive
% simplify_intern_and(X,Y,false,true) :-
% negate_atom(X,X2),
% occurs_check_and(Y,X2),
% !.
simplify_intern_and(X,Y,(X2,Y2),Result) :-
!,
simplify_intern(X,X2,Result1),
simplify_intern(Y,Y2,Result2),
or(Result1,Result2,Result).
%-----------
simplify_intern_implication(true,Y,Y,true) :-
!.
simplify_intern_implication(false,Y,(\+ Y),true) :-
!.
simplify_intern_implication(X,true,X,true) :-
!.
simplify_intern_implication(X,false,(\+ X),true) :-
!.
simplify_intern_implication(X,Y,(X <=> Y2), Result) :-
!,
simplify_intern(Y,Y2,Result).
%-----------
simplify_intern_negation(true,false,true).
simplify_intern_negation(false,true,true).
simplify_intern_negation((\+ X),X,true).
simplify_intern_negation((A,B),Term,true) :-
simplify_intern_or( (\+ A), (\+ B), Term, _).
simplify_intern_negation((A;B),Term,true) :-
simplify_intern_and( (\+ A), (\+ B), Term, _).
simplify_intern_negation('$atom'(X),(\+ '$atom'(X)),false).
%========================================================================
%=
%=
%= list_to_disjunction(+List,-Disjunction)
%========================================================================
list_to_disjunction([A,B|T],(A;T2)) :-
!,
list_to_disjunction([B|T],T2).
list_to_disjunction([A],A).
list_to_disjunction([],false).
%========================================================================
%=
%=
%= list_to_conjunction(+List,(A,T2)-Conjunction) :-
%========================================================================
list_to_conjunction([A,B|T],(A,T2)) :-
!,
list_to_conjunction([B|T],T2).
list_to_conjunction([A],A).
list_to_conjunction([],true).