// compare each cnf with other
public void CompareCNF(CNFSentences first, CNFSentences second, List <CNFSentences> addKB)
{
if (first.symbol == null && second.symbol == null)
{
foreach (CNFSentences f in first.children)
{
foreach (CNFSentences s in second.children)
{
if (f.symbol == s.symbol && f.Negate != s.Negate)
{
addKB.Add(RetureNewStatement(first, second, f.symbol));
}
}
}
}
else if (first.symbol != null && second.symbol == null)
{
foreach (CNFSentences s in second.children)
{
if (s.symbol == first.symbol && s.Negate != first.Negate)
{
addKB.Add(RetureNewStatement2(first, second));
}
}
}
else if (first.symbol == null && second.symbol != null)
{
CompareCNF(second, first, addKB);
}
}
// joins 2 cnf sentenses both with children
public CNFSentences RetureNewStatement(CNFSentences first, CNFSentences second, string common)
{
Dictionary <string, bool> temp = new Dictionary <string, bool>();
temp.Clear();
foreach (CNFSentences f in first.children)
{
if (f.symbol != common)
{
temp.Add(f.symbol, f.Negate);
}
}
foreach (CNFSentences s in second.children)
{
if (s.symbol != common && !temp.ContainsKey(s.symbol))
{
temp.Add(s.symbol, s.Negate);
}
}
if (temp.Count == 1)
{
foreach (KeyValuePair <string, bool> k in temp)
{
return(new CNFSentences(k.Key, k.Value));
}
}
return(new CNFSentences(temp));
}
public CNFSentences(Dictionary <string, bool> temp)
{
children = new CNFSentences[temp.Count];
int i = 0;
foreach (KeyValuePair <string, bool> kv in temp)
{
children[i++] = new CNFSentences(kv.Key, kv.Value);
}
}
public void PrintResult(List <CNFSentences> KB, CNFSentences alpha)
{
Console.WriteLine("All CNF KBs\n");
foreach (CNFSentences c in KB)
{
Print(c);
}
Console.WriteLine("\nKB and ~ alpha is unsatisfiable\n");
}
// checks if KB has d when alpha is ~d
public bool CheckSolved(List <CNFSentences> KB, CNFSentences alpha)
{
foreach (CNFSentences c in KB)
{
if (c.symbol != null && c.symbol == alpha.symbol)
{
return(!(c.Negate == alpha.Negate));
}
}
return(false);
}
// check if the newCNF is alredy in the list or not
public bool ContainsKB(List <CNFSentences> KB, CNFSentences newCNF)
{
foreach (CNFSentences cnf in KB)
{
if (!NotSame(cnf, newCNF))
{
return(true);
}
}
return(false);
}
public void PrintEach(CNFSentences c)
{
if (c.Negate)
{
Console.Write("~");
}
if (c.symbol != null)
{
Console.Write(c.symbol);
}
}
public Resolution(string fileName) : base(fileName)
{
CNF cnf = new CNF(hornFormKB.KB);
List <CNFSentences> KB = new List <CNFSentences>(cnf.CNFKB);
CNFSentences alpha = new CNFSentences(hornFormKB.query.symbol, true);
if (QueryNotSolvable(KB, alpha))
{
Console.WriteLine("NO");
}
else
{
PLResolution(KB, alpha);
}
}
public bool PLResolution(List <CNFSentences> KB, CNFSentences alpha)
{
List <CNFSentences> addKB = new List <CNFSentences>();
bool loop = false;
loop = CheckSolved(KB, alpha);
if (loop)
{
print.PrintResult(KB, alpha);
}
if (loop)
{
Console.WriteLine("YES"); return(true);
}
addKB.Clear();
// compare each CNF with every other CNF
for (int i = 0; i < KB.Count - 1; i++)
{
for (int j = i + 1; j < KB.Count; j++)
{
CompareCNF(KB[i], KB[j], addKB);
}
}
// if no new CNF added then return NO
int x = 0;
foreach (CNFSentences c in addKB)
{
if (!ContainsKB(KB, c))
{
x++;
KB.Add(c);
}
}
if (x == 0)
{
Console.WriteLine("NO"); return(false);
}
PLResolution(KB, alpha);
return(false);
}
// if ASK symbol is not in KB
public bool QueryNotSolvable(List <CNFSentences> KB, CNFSentences alpha)
{
foreach (CNFSentences c in KB)
{
if (c.symbol != null && c.symbol == alpha.symbol)
{
return(false);
}
if (c.symbol == null)
{
foreach (CNFSentences child in c.children)
{
if (child.symbol != null && child.symbol == alpha.symbol)
{
return(false);
}
}
}
}
return(true);
}
//
public bool NotSame(CNFSentences first, CNFSentences second)
{
if (first.symbol == null && second.symbol == null && first.children.Length != second.children.Length)
{
return(true);
}
else if (first.symbol == null && second.symbol == null && first.children.Length == second.children.Length)
{
for (int i = 0; i < first.children.Length; i++)
{
if (first.children[i].symbol != second.children[i].symbol)
{
return(true);
}
}
}
else if (first.symbol != null && second.symbol != null)
{
if (first.symbol != second.symbol)
{
return(true);
}
else if (first.Negate != second.Negate)
{
return(true);
}
}
else if (first.symbol == null && second.symbol != null)
{
return(true);
}
else if (first.symbol != null && second.symbol == null)
{
return(true);
}
return(false);
}
// prints each CNFSentence
public void Print(CNFSentences c)
{
if (c.symbol != null)
{
if (c.Negate)
{
Console.Write("~");
}
Console.Write(c.symbol);
}
else if (c.children.Length == 2)
{
if (c.children[0].Negate)
{
Console.Write("~");
}
Console.Write(c.children[0].symbol);
Console.Write(" v ");
Console.Write(c.children[1].symbol);
}
else if (c.children.Length == 3)
{
if (c.children[0].Negate)
{
Console.Write("~");
}
Console.Write(c.children[0].symbol);
Console.Write(" v ");
if (c.children[1].Negate)
{
Console.Write("~");
}
Console.Write(c.children[1].symbol);
Console.Write(" v ");
Console.Write(c.children[2].symbol);
}
else if (c.children.Length == 1)
{
if (c.children[0].Negate)
{
Console.Write("~");
}
Console.Write(c.children[0].symbol);
}
else if (c.children.Length == 4)
{
if (c.children[0].Negate)
{
Console.Write("~");
}
Console.Write(c.children[0].symbol);
Console.Write(" v ");
if (c.children[1].Negate)
{
Console.Write("~");
}
Console.Write(c.children[1].symbol);
Console.Write(" v ");
if (c.children[2].Negate)
{
Console.Write("~");
}
Console.Write(c.children[2].symbol);
Console.Write(" v ");
if (c.children[3].Negate)
{
Console.Write("~");
}
Console.Write(c.children[3].symbol);
}
else if (c.children.Length > 4)
{
bool or = false;
for (int i = 0; i < c.children.Length; i++)
{
if (or)
{
Console.Write(" v ");
}
PrintEach(c.children[i]);
or = true;
}
//Console.ReadLine();
}
Console.WriteLine();
}
