/// <summary>
/// Applies backwards the relevant operator effects and operator preconditions to the given target relative state.
/// </summary>
/// <param name="relativeState">Target relative state to be modified.</param>
/// <param name="operatorSubstitution">Variables substitution.</param>
/// <returns>Preceding relative states.</returns>
public IEnumerable <Planner.IRelativeState> ApplyBackwards(IRelativeState relativeState, ISubstitution operatorSubstitution)
{
OperatorSubstitution = operatorSubstitution;
Effects.GroundEffectsByCurrentOperatorSubstitution(GroundingManager, operatorSubstitution);
relativeState = (IRelativeState)relativeState.Clone();
// prepare operator preconditions
var operatorPreconditions = (OperatorPreconditions != null) ? GroundingManager.GroundConditions(ClearRigidRelations(OperatorPreconditions), OperatorSubstitution) : null;
// remove positively contributing effects from the relative state and insert the operator preconditions
ProcessPrimitiveEffects(relativeState);
relativeState = ProcessForallEffects(relativeState);
foreach (var resultState in ProcessWhenEffects(relativeState))
{
if (operatorPreconditions != null)
{
foreach (var modifiedResultState in ProcessOperatorPreconditions(operatorPreconditions, resultState))
{
yield return(modifiedResultState);
}
}
else
{
yield return(resultState);
}
}
}
/// <summary>
/// Applies the operator backwards to the given target relative state. The result is a new relative state (or more relative states, if conditional effects are present).
/// </summary>
/// <param name="relativeState">Relative state for the application.</param>
/// <param name="operatorPreconditions">Operator preconditions.</param>
/// <returns>Preceding relative states.</returns>
public IEnumerable <IRelativeState> ApplyBackwards(IRelativeState relativeState, ISimpleConditions operatorPreconditions)
{
IRelativeState result = (IRelativeState)relativeState.Clone();
bool anyConditionalEffect = false;
foreach (var effect in this)
{
if (effect.GetConditions() == null)
{
result = effect.ApplyBackwards(result);
}
else
{
anyConditionalEffect = true;
}
}
foreach (var constraint in operatorPreconditions)
{
result.SetValue(constraint.GetVariable(), constraint.GetValue());
}
if (!anyConditionalEffect)
{
yield return(result);
}
else
{
List <IRelativeState> states = new List <IRelativeState> {
result
};
foreach (var effect in this)
{
if (effect.GetConditions() != null)
{
int statesCount = states.Count;
for (int i = 0; i < statesCount; ++i)
{
var newEffect = effect.ApplyBackwards(states[i]);
if (newEffect != null)
{
states.Add(newEffect);
}
}
}
}
foreach (var state in states)
{
yield return(state);
}
}
}
/// <summary>
/// Applies the effect backwards to the given relative state.
/// </summary>
/// <param name="relativeState">Relative state.</param>
public override IRelativeState ApplyBackwards(IRelativeState relativeState)
{
// we explicitly apply the effect for the relative state, if it's relevant
if (IsRelevant(relativeState) == EffectRelevance.RELEVANT)
{
var newState = (IRelativeState)relativeState.Clone();
newState.SetValue(Assignment.GetVariable(), RelativeState.WildCardValue);
foreach (var constraint in Conditions)
{
newState.SetValue(constraint.GetVariable(), constraint.GetValue());
}
return(newState);
}
// the conditional effect was not applied, because it was not relevant
return(null);
}
/// <summary>
/// Generates all possible PDDL relative states meeting given CNF conditions (in the form of a list of conjuncts). Lazy generated recursively via yield return.
/// </summary>
/// <param name="index">Current index in the conjuncts list.</param>
/// <param name="conjuncts">List of conjuncts of the CNF conditions.</param>
/// <param name="result">Current relative state being built.</param>
/// <returns>All possible PDDL relative states meeting the CNF conditions.</returns>
private static IEnumerable <IRelativeState> EnumerateRelativeStatesByCNF(int index, List <IConjunctCNF> conjuncts, IRelativeState result)
{
if (index == 0)
{
// the constructed state can have trailing values from the previous unfinished enumeration!
result.ClearContent();
}
Action <IRelativeState, LiteralCNF> addLiteral = (state, literal) =>
{
// Note: At the moment, there is limited support for object and numeric function assignments.
// For example, numeric comparison literals like (< (numFunc) 5) will be omitted in the resulting relative state.
PredicateLiteralCNF predicateLiteral = literal as PredicateLiteralCNF;
if (predicateLiteral != null)
{
if (literal.IsNegated)
{
state.AddNegatedPredicate(predicateLiteral.PredicateAtom.Clone());
}
else
{
state.AddPredicate(predicateLiteral.PredicateAtom.Clone());
}
return;
}
EqualsLiteralCNF equalsLiteral = literal as EqualsLiteralCNF;
if (equalsLiteral != null)
{
var assignment = equalsLiteral.TryGetObjectFunctionAssignment();
if (assignment != null)
{
if (!literal.IsNegated)
{
state.AssignObjectFunction(assignment.Item1.FunctionAtom.Clone(), assignment.Item2.NameId);
}
}
return;
}
NumericCompareLiteralCNF compareLiteral = literal as NumericCompareLiteralCNF;
if (compareLiteral != null)
{
var assignment = compareLiteral.TryGetNumericFunctionAssignment();
if (assignment != null)
{
if (!compareLiteral.IsNegated)
{
state.AssignNumericFunction(assignment.Item1.FunctionAtom.Clone(), assignment.Item2.Value);
}
}
}
};
Action <IRelativeState, LiteralCNF> removeLiteral = (state, literal) =>
{
PredicateLiteralCNF predicateLiteral = literal as PredicateLiteralCNF;
if (predicateLiteral != null)
{
if (literal.IsNegated)
{
state.RemoveNegatedPredicate(predicateLiteral.PredicateAtom.Clone());
}
else
{
state.RemovePredicate(predicateLiteral.PredicateAtom.Clone());
}
return;
}
EqualsLiteralCNF equalsLiteral = literal as EqualsLiteralCNF;
if (equalsLiteral != null)
{
var assignment = equalsLiteral.TryGetObjectFunctionAssignment();
if (assignment != null)
{
if (!literal.IsNegated)
{
state.AssignObjectFunction(assignment.Item1.FunctionAtom.Clone(), ObjectFunctionTerm.UndefinedValue);
}
}
return;
}
NumericCompareLiteralCNF compareLiteral = literal as NumericCompareLiteralCNF;
if (compareLiteral != null)
{
var assignment = compareLiteral.TryGetNumericFunctionAssignment();
if (assignment != null)
{
if (!compareLiteral.IsNegated)
{
state.AssignNumericFunction(assignment.Item1.FunctionAtom.Clone(), NumericFunction.UndefinedValue);
}
}
}
};
if (index >= conjuncts.Count)
{
yield return((IRelativeState)result.Clone());
}
else
{
var conjunct = conjuncts[index];
ClauseCNF clause = conjunct as ClauseCNF;
if (clause != null)
{
foreach (var literal in clause)
{
addLiteral(result, literal);
foreach (var item in EnumerateRelativeStatesByCNF(index + 1, conjuncts, result))
{
yield return(item);
}
removeLiteral(result, literal);
}
}
else
{
LiteralCNF literal = conjunct as LiteralCNF;
Debug.Assert(literal != null);
addLiteral(result, literal);
foreach (var item in EnumerateRelativeStatesByCNF(index + 1, conjuncts, result))
{
yield return(item);
}
removeLiteral(result, literal);
}
}
}