/// <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>
/// Grounds the specified conditions by a minimal needed operator substitution.
/// </summary>
/// <param name="conditions">Conditions.</param>
/// <returns>Grounded conditions.</returns>
private Conditions GroundConditions(Conditions conditions)
{
return(GroundingManager.GroundConditions(conditions, IsApplicationLifted ? ExtractMinimalOperatorSubstitution() : OperatorSubstitution));
}
