public override Proposition Nandify()
{
Negation negationOfLeftSuccessor = new Negation();
negationOfLeftSuccessor.LeftSuccessor = LeftSuccessor;
Negation negationOfRighSuccessor = new Negation();
negationOfRighSuccessor.LeftSuccessor = RightSuccessor;
Conjunction leftDisjunctionConjunct = new Conjunction();
leftDisjunctionConjunct.LeftSuccessor = negationOfLeftSuccessor;
leftDisjunctionConjunct.RightSuccessor = negationOfRighSuccessor;
Conjunction rightDisjunctionConjunct = new Conjunction();
rightDisjunctionConjunct.LeftSuccessor = LeftSuccessor;
rightDisjunctionConjunct.RightSuccessor = RightSuccessor;
Disjunction disjunction = new Disjunction();
disjunction.LeftSuccessor = leftDisjunctionConjunct;
disjunction.RightSuccessor = rightDisjunctionConjunct;
return(disjunction.Nandify());
}
private void CreateConnective(char connective)
{
Proposition result = null;
// 'GetCorrespondingConnective'
switch (connective)
{
case Negation.SYMBOL:
result = new Negation();
break;
case Implication.SYMBOL:
result = new Implication();
break;
case BiImplication.SYMBOL:
result = new BiImplication();
break;
case Conjunction.SYMBOL:
result = new Conjunction();
break;
case Disjunction.SYMBOL:
result = new Disjunction();
break;
case Nand.SYMBOL:
result = new Nand();
break;
case UniversalQuantifier.SYMBOL:
result = new UniversalQuantifier(PopBoundVariable());
break;
case ExistentialQuantifier.SYMBOL:
result = new ExistentialQuantifier(PopBoundVariable());
break;
}
// 'CreateExpression'
// The symbols[symbols.Count - 1] can always be done. Placement is dependent on Unary or Binary connective.
if (result is BinaryConnective)
{
((BinaryConnective)result).LeftSuccessor = symbols[symbols.Count - 2];
((BinaryConnective)result).RightSuccessor = symbols[symbols.Count - 1];
symbols.RemoveAt(symbols.Count - 1);
symbols.RemoveAt(symbols.Count - 1);
}
else
{
((UnaryConnective)result).LeftSuccessor = symbols[symbols.Count - 1];
symbols.RemoveAt(symbols.Count - 1);
}
// Now the expression is a symbol in case a nested connective needs to use it
// as right or left successor.
symbols.Add(result);
}
public override Proposition Copy()
{
Disjunction copy = new Disjunction();
copy.LeftSuccessor = LeftSuccessor.Copy();
copy.RightSuccessor = RightSuccessor.Copy();
return(copy);
}
public override Proposition Nandify()
{
Negation negation = new Negation();
negation.LeftSuccessor = LeftSuccessor;
Disjunction disjunction = new Disjunction();
disjunction.LeftSuccessor = negation;
disjunction.RightSuccessor = RightSuccessor;
return(disjunction.Nandify());
}
public static Proposition CreateTautologyFromProposition(Proposition variable)
{
if (variable == null)
{
throw new NullReferenceException("A proposition is required to create a tautology from it!");
}
Disjunction tautology = new Disjunction();
tautology.LeftSuccessor = variable; // A
Negation negatedVariable = new Negation();
negatedVariable.LeftSuccessor = variable;
tautology.RightSuccessor = negatedVariable; // A | ~(A) == 1
return(tautology);
}
private List <Proposition> CreateCorrespondingDisjuncts(List <Proposition> propositionList)
{
while (propositionList.Count > 1)
{
Disjunction disjunct = new Disjunction();
disjunct.LeftSuccessor = propositionList[0];
disjunct.RightSuccessor = propositionList[1];
propositionList.RemoveAt(1);
propositionList.RemoveAt(0);
propositionList.Add(disjunct);
}
return(propositionList);
}