static void Main(string[] args)
{
Clauses C = new Clauses();
//add KB to Clauses in CNF form
C.Add(new List <string> {
"a", "!b"
}); //a+!b
C.Add(new List <string> {
"b", "!c", "!d"
}); //b+!c+!d
C.Add(new List <string> {
"b", "c", "!d"
}); //b+c+!d
C.Add(new List <string> {
"d"
}); //d
//CHANGE THIS LINE TO CHECK OTHER LITERALS
List <string> formula = new List <string>()
{
"!b"
}; //define as CNF, KB:=a --> formula/clause = !a to proof nonsatisfaction,
Console.WriteLine(C.Print() + " =: " + formula[0]);
//Console.ReadLine();
//bool enumerates = Algorithm.linearResolution(C, new List<string>(formula));
bool enumerates = Algorithm.Astar(C, formula);
Console.WriteLine("KB := !" + C.Print(formula) + " is " + enumerates.ToString());
Console.ReadLine();
}
public List <Node> getChildren()
{
List <Node> children = new List <Node>();
for (int i = 0; i < Kb.allClauses.Count; i++)
{
if (canSolve(Kb.allClauses[i]))
{
var clause1 = new List <string>(Kb.allClauses[i]);
var clause2 = new List <string>(ResolvedClause);
var solvedClause = Algorithm.resolutionRule(clause1, clause2, out int heuristic);
//Kb.allClauses.Add(solvedClause);
var tempKb = new Clauses {
allClauses = new List <List <string> >(Kb.allClauses)
};
tempKb.allClauses.Add(ResolvedClause);
//Need to add pathCost
var node = new Node()
{
Kb = tempKb, //I wonder if it works, since syntax is a bit weird xD
parent = this,
ResolvedClause = solvedClause,
Cost = Cost + heuristic
};
children.Add(node);
}
}
return(children);
}
//it is like Uniform cost search, but we have an ordered queue
//path cost is set in problem class..
// algo from Book: figure 3.14
public static Boolean Astar(Clauses kb, List <string> formula)
{
//Node node = new Node(problem.initial(), null, null, 0);
var node = new Node
{
Kb = kb,
ResolvedClause = formula,
Cost = 0
};
List <Node> frontier = new List <Node>(); //priority queue
frontier.Add(node);
List <Node> expanded = new List <Node>();
var index = 0;
while (frontier.Any())
{
frontier.OrderBy(x => x.Cost); //orders frontier in ascending order
node = frontier[0]; //picks the one with lowest value
Console.WriteLine(node.Kb.Print() + " =: " + node.Kb.Print(node.ResolvedClause));
//Console.WriteLine("current node: " + node.State().print());
if (node.Kb.allClauses.Count == 0 || frontier.Exists(x => x.ResolvedClause.Count() == 0))
{
return(true);
}
frontier.Remove(node);
expanded.Add(node);
foreach (Node child in node.getChildren())
{ //if child state not in frontier and not in expanded
if ((!frontier.Exists(x => x.Kb == child.Kb)))
{
if (!expanded.Exists(x => x.Kb == child.Kb))
{
frontier.Add(child);
}
}
else//here we know that chil is in frontier, as above if failed.
{ //if node already exist in frontier, but child can reach it wirh less cost, then replace node in frontier.
int i = frontier.FindIndex(x => x.Kb == child.Kb);
if (frontier[i].Cost > child.Cost)
{
frontier[i] = child;
}
}
}
}
Console.WriteLine("\n" + "Frontier is empty, no solution found.");
return(false); //if frontier is empty
}