public static List<GrammarRule> AugmentGrammar(List<GrammarRule> theGrammar)
{
List<GrammarRule> AugmentedGrammar = new List<GrammarRule>();
GrammarRule FirstRule = theGrammar[0];
if (!FirstRule.Expression[FirstRule.Expression.Count - 1].Equals(getEndSymbol()))
{
String ExtraRuleName = FirstRule.RuleSymbol.id + "'";
Symbol[] ExtraRuleExpression = new Symbol[] { new Symbol(FirstRule.RuleSymbol.id), getEndSymbol() };
GrammarRule ExtraRule = new GrammarRule(ExtraRuleName, ExtraRuleExpression);
AugmentedGrammar.Add(ExtraRule);
}
foreach (GrammarRule rule in theGrammar)
{
AugmentedGrammar.Add(rule);
}
return AugmentedGrammar;
}
private static HashSet<Symbol> Follow(Symbol B, List<GrammarRule> theGrammar)
{
HashSet<Symbol> result = new HashSet<Symbol>();
foreach (GrammarRule rule in theGrammar)
{
if (rule.Expression.Contains(B))
{
for (int i = 0; i < rule.Expression.Count; i++) // iterate through every expression member
{
if (rule.Expression[i].Equals(B)) // if it's equal to our symbol...
{
bool isEpsylon = true;
for (int j = i + 1; j < rule.Expression.Count; j++) // iterate through reamining members
{ // check if they are all epsylon
isEpsylon = isEpsylon && rule.Expression[j].Equals(Lr0GenerationHelper.getEpsylonSymbol());
}
if (!isEpsylon)
{ // if rest is not epsylon
List<Symbol> RemainingSymbols = rule.Expression.GetRange(i + 1, rule.Expression.Count - (i + 1));
HashSet<Symbol> FirstSet = First(RemainingSymbols, theGrammar);
FirstSet.Remove(Lr0GenerationHelper.getEpsylonSymbol());
result.UnionWith(FirstSet);
}
if (i == rule.Expression.Count - 1) // if it's the final production
{
if (!rule.RuleSymbol.Equals(B))
result.UnionWith(Follow(rule.RuleSymbol, theGrammar));
}
else
{
List<Symbol> RemainingSymbols = rule.Expression.GetRange(i + 1, rule.Expression.Count - (i + 1));
if (First(RemainingSymbols, theGrammar).Contains(Lr0GenerationHelper.getEpsylonSymbol()))
{
if (!rule.RuleSymbol.Equals(B))
result.UnionWith(Follow(rule.RuleSymbol, theGrammar));
}
}
}
}
}
}
return result;
}
private static HashSet<Symbol> First(Symbol X, List<GrammarRule> theGrammar)
{
HashSet<Symbol> result = new HashSet<Symbol>();
if (X.isTerminal) result.Add(X); //If it's terminal.. just add it
else
{
foreach (GrammarRule rule in theGrammar)
{
if (X.Equals(rule.RuleSymbol)) // if productions looks like X --> _______
{
if (rule.Expression[0].isTerminal)
{
result.Add(rule.Expression[0]);
}
else
{
HashSet<Symbol> YsFirst = First(rule.Expression, theGrammar);
result.UnionWith(YsFirst);
}
}
}
}
return result;
}
public static Lr0State Goto(Lr0State theState, Symbol inputSymbol, List<GrammarRule> theGrammar)
{
List<Item> generatedItems = theState.GetGotoItems(inputSymbol);
Lr0State resultState = new Lr0State(generatedItems);
return Closure(resultState, theGrammar);
}
public List<Item> GetGotoItems(Symbol theSymbol)
{
List<Item> ResultSet = new List<Item>();
foreach (Item Production in itemSet)
{
if (!Production.isFinal())
{
if (Production.getCurrentSymbol().Equals(theSymbol))
{
Item ItemToAdd = new Item(Production.Rule, Production.Position + 1);
ResultSet.Add(ItemToAdd);
}
}
}
return ResultSet;
}
public GrammarRule(string theName, Symbol[] theExpression)
{
RuleSymbol = new Symbol(theName);
Expression = new List<Symbol>(theExpression);
}