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plasp/encodings/pddl-meta-sequential-incremental.lp

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#include <incmode>.
#program base.
% Establish initial state
holds(Predicate, 0) :- initialState(Predicate).
#program step(t).
% Perform actions
1 {occurs(action(Action), t) : action(Action)} 1.
% Check preconditions
:- occurs(Action, t), precondition(Action, Predicate, true), not holds(Predicate, t - 1).
:- occurs(Action, t), precondition(Action, Predicate, false), holds(Predicate, t - 1).
% Apply effects
caused(Predicate, true, t) :- occurs(Action, t), postcondition(Action, Predicate, true).
caused(Predicate, false, t) :- occurs(Action, t), postcondition(Action, Predicate, false).
holds(Predicate, t) :- caused(Predicate, true, t).
holds(Predicate, t) :- holds(Predicate, t - 1), not caused(Predicate, false, t).
#program check(t).
% Verify that goal is met
:- query(t), goal(Predicate, true), not holds(Predicate, t).
:- query(t), goal(Predicate, false), holds(Predicate, t).
#show query/1.
#show occurs/2.