/// <summary>Convert to CNF proposition</summary>
/// <exception cref="InvaildPropositionException"></exception>
/// <returns>CNF proposition</returns>
public static Proposition ToCNF(this Proposition expr)
{
if (expr.IsCNF())
{
return(expr);
}
if (expr.IsNNF())
{
return(logEngine.ConvertToCNF(expr));
}
else
{
return(logEngine.ConvertToCNF(logEngine.ConvertToNNF(expr)));
}
}
