private Policy BestRemoval(LogicalForm l)
{
// first, we find what supports l.
if (!activeRules.ContainsKey(l))
{
// this means l was not inferred.
// What should we do here?
return(new Remove(l));
}
foreach (Rule r in activeRules[l].Item2)
{
HashSet <LogicalForm> top = r.GetTop();
HashSet <LogicalForm>[] bot = r.GetBottom();
// all the rules where l is on bottom
// we can either side-step or remove a top one
Policy bestRemoval = null;
Policy bestShift = null;
if (top.Count > 0)
{
bestRemoval = BestRemoval(top.First());
// determine best top to remove
foreach (LogicalForm parent in top)
{
Policy contender = BestRemoval(parent);
if (CompareLikelihood(bestRemoval, contender) < 0)
{
bestRemoval = contender;
}
}
}
// THIS IS ALL THE SIDE-STEP STUFF
for (int i = 0; i < bot.Length; i++)
{
HashSet <LogicalForm> currentTier = bot[i];
foreach (LogicalForm sibling in currentTier)
{
if (!Satisfies(sibling.Negate()))
{
if (bestShift == null)
{
bestShift = BestAddition(sibling);
}
else
{
int comparitor = CompareLikelihood(bestShift, BestAddition(sibling));
if (comparitor < 0)
{
bestShift = BestAddition(sibling);
}
}
}
}
if (bestShift != null)
{
break;
}
}
// bestRemoval = bestRemoval.Concat(new Remove(l));
bestShift = bestRemoval.GetDual().Concat(bestShift);
Policy winner = (CompareLikelihood(bestRemoval, bestShift) > 0) ? bestRemoval : bestShift;
return(winner.Concat(new Remove(l)));
}
return(null);
// TODO collect best results from different rules
}