public SymbolValuePair FindPureSymbolValuePair(IList <Sentence> clauseList,
Model model)
{
IList <Sentence> clausesWithNonTrueValues = ClausesWithNonTrueValues(clauseList, model);
Sentence nonTrueClauses = LogicUtils.ChainWith("AND", clausesWithNonTrueValues);
// System.out.println("Unsatisfied clauses = "
// + clausesWithNonTrueValues.Count);
ISet <Symbol> symbolsAlreadyAssigned = model.GetAssignedSymbols();
// debug
// IList symList = asList(symbolsAlreadyAssigned);
//
// System.out.println(" assignedSymbols = " + symList.Count);
// if (symList.Count == 52) {
// System.out.println("untrue clauses = " + clausesWithNonTrueValues);
// System.out.println("model= " + model);
// }
// debug
IList <Symbol> purePositiveSymbols = new SymbolClassifier().GetPurePositiveSymbolsIn(nonTrueClauses)
.Except(symbolsAlreadyAssigned).ToList();
IList <Symbol> pureNegativeSymbols =
new SymbolClassifier().GetPureNegativeSymbolsIn(nonTrueClauses).Except(symbolsAlreadyAssigned).ToList();
// if none found return "not found
if ((purePositiveSymbols.Count == 0) &&
(pureNegativeSymbols.Count == 0))
{
return(new SymbolValuePair());// automatically set to null values
}
else
{
if (purePositiveSymbols.Count > 0)
{
Symbol symbol = new Symbol((purePositiveSymbols[0])
.Value);
if (pureNegativeSymbols.Contains(symbol))
{
throw new ApplicationException("Symbol " + symbol.Value
+ "misclassified");
}
return(new SymbolValuePair(symbol, true));
}
else
{
Symbol symbol = new Symbol((pureNegativeSymbols[0])
.Value);
if (purePositiveSymbols.Contains(symbol))
{
throw new ApplicationException("Symbol " + symbol.Value
+ "misclassified");
}
return(new SymbolValuePair(symbol, false));
}
}
}
private Sentence CreateResolventClause(ClauseSymbols cs, Symbol toRemove)
{
var positiveSymbols = cs.Clause1PositiveSymbols.Union(cs.Clause2PositiveSymbols).ToList();
var negativeSymbols = cs.Clause1NegativeSymbols.Union(cs.Clause2NegativeSymbols).ToList();
if (positiveSymbols.Contains(toRemove))
{
positiveSymbols.Remove(toRemove);
}
if (negativeSymbols.Contains(toRemove))
{
negativeSymbols.Remove(toRemove);
}
positiveSymbols.Sort(this.CompareSymbols);
negativeSymbols.Sort(this.CompareSymbols);
IList <Sentence> sentences = new List <Sentence>();
for (int i = 0; i < positiveSymbols.Count; i++)
{
sentences.Add(positiveSymbols[i]);
}
for (int i = 0; i < negativeSymbols.Count; i++)
{
sentences.Add(new UnarySentence(negativeSymbols[i]));
}
if (sentences.Count == 0)
{
return(new Symbol("EMPTY_CLAUSE")); // == empty clause
}
else
{
return(LogicUtils.ChainWith("OR", sentences));
}
}
public Sentence AsSentence()
{
return(LogicUtils.ChainWith("AND", this.Sentences));
}