/// <summary>Check this proposition is conjunction normal form</summary>
/// <returns>True if CNF</returns>
public bool IsCNF()
{
if (!IsNNF())
{
return(false);
}
if (op == Operator.Atom)
{
return(true);
}
else if (op == Operator.Not)
{
return(left.op == Operator.Atom);
}
else if (op == Operator.And)
{
return(left.IsCNF() && right.IsCNF());
}
else if (op == Operator.Or)
{
return(this.IsClause());
}
else
{
return(false);
}
}
/// <summary>Check whether give proposition is tautology</summary>
/// <param name="expr">Proposition to check</param>
/// <exception cref="InvaildPropositionException"></exception>
/// <returns>True if tautology</returns>
public bool IsTautology(Proposition expr)
{
if (expr == null || !expr.IsVaild())
{
throw new InvalidPropositionException("INVAILD");
}
if (!expr.IsCNF())
{
expr = ConvertToCNF(ConvertToNNF(expr));
}
return(IsTautologyCore(expr));
}