public override bool SolveAndQuery(string symbol)
{
//Initialize
List <string> literalsToSolve = new List <string>();
literalsToSolve.Add(symbol);
List <HornRule> rulesToSolve = new List <HornRule>();
List <HornRule> checkedRules = new List <HornRule>();
bool stateChanged = true;
while (stateChanged == true)
{
stateChanged = false;
//Add the the list of rules to solve any rules which are relevant to our query (I.e. are relevant to symbols which are relevant).
//Then add each symbol used by those rules to the list of literals to solve.
foreach (HornRule HR in KB)
{
if (checkedRules.Contains(HR))
{
continue;
}
for (int i = 0; i < literalsToSolve.Count; ++i)
{
if (HR.LiteralIsImplication(literalsToSolve[i]))
{
stateChanged = true;
rulesToSolve.Add(HR);
checkedRules.Add(HR);
foreach (string s in HR.symbols)
{
if (!literalsToSolve.Contains(s))
{
literalsToSolve.Add(s);
}
}
break;
}
}
}
//Try to solve each of the rules given the current knowledge.
//If a rule is solved, remove it from the list, and add any symbols it entails to the KB.
for (int r = 0; r < rulesToSolve.Count; ++r)
{
//Resolve the rule. If it was fully resolved:
rulesToSolve[r].Resolve(literalsKey, literalsSolutions);
if (rulesToSolve[r].IsFullyResolved)
{
//If this rule proves a literal (i.e. doesn't return Unknown), add the literal to the knowledge and remove the rule.
HornRule.Literal newLiteral = rulesToSolve[r].ProveLiteral(literalsKey, literalsSolutions);
if (newLiteral.state != SymbolIs.Unknown)
{
stateChanged = true;
//Loop through the knowledge table and add the new information at the correct index.
for (int i = 0; i < literalsKey.Length; ++i)
{
if (literalsKey[i] == newLiteral.symbol)
{
if (literalsSolutions[i] == SymbolIs.Unknown)
{
literalsSolutions[i] = newLiteral.state;
}
else if (literalsSolutions[i] != newLiteral.state)
{
throw new Exception("KnowledgeBase is contradictory");
}
}
}
//If the symbol being proven is the query symbol, return true.
if (newLiteral.symbol == symbol)
{
return(true);
}
//Stop trying to find rules relevant to the proven literal.
literalsToSolve.Remove(newLiteral.symbol);
//Remove the solved rule from the list, and go back one index.
rulesToSolve.RemoveAt(r);
--r;
}
}
}
} //End of While loop.
return(false);
}
