private List <GrammarItem> Closure(List <GrammarItem> items)
{
List <GrammarItem> I = new List <GrammarItem>();
I.AddRange(items);
for (int i = 0; i < I.Count; i++)
{
var item = I[i];
if (item.IsHightlightAfterFinalEntry)
{
continue;
}
if (item.HighlightedEntry.IsTerminal)
{
continue;
}
var nt = item.HighlightedEntry as NonTerminal;
var afterHighlight = item.EntriesAfterHighlight;
foreach (var l in item.Lookaheads)
{
ProductionEntry[] afterPlusLookahead = new ProductionEntry[afterHighlight.Length + 1];
Array.Copy(afterHighlight, afterPlusLookahead, afterHighlight.Length);
afterPlusLookahead[^ 1] = l;
private void SetAction(ParserState state, ProductionEntry key, ParserAction newAction)
{
if (key is NonTerminal nt)
{
Console.WriteLine();
}
if (state.Action.ContainsKey(key.ID))
{
var oldAction = state.Action[key.ID];
if (oldAction.ToString() == newAction.ToString())
{
return;
}
if (!(oldAction is AcceptAction) && !(newAction is AcceptAction))
{
if (oldAction.Name != newAction.Name)
{
//Shift/Reduce Conflict
ShiftAction shiftAction = (oldAction.Name == "shift" ? oldAction : newAction) as ShiftAction;
ReduceAction reduceAction = (oldAction.Name == "shift" ? newAction : oldAction) as ReduceAction;
var prod = reduceAction.Production;
var term = key as Terminal;
//Resolve based on precedence and associativity
if (prod.Precendece > term.Precedence ||
(prod.Precendece == term.Precedence && prod.Associatvity == OperatorAssociativity.Left))
{
state.Action[key.ID] = reduceAction;
}
else
{
state.Action[key.ID] = shiftAction;
}
return;
}
else if (newAction is ReduceAction)
{
//Reduce/Reduce conflict
var newProd = (newAction as ReduceAction).Production;
var oldProd = (oldAction as ReduceAction).Production;
bool newFirst = false;
if (newProd.Lhs != oldProd.Lhs)
{
//Find the NonTerminal to appear first
newFirst = newProd.Lhs.ID < oldProd.Lhs.ID;
}
else
{
//Find the production to appear first
foreach (var p in newProd.Lhs.Productions)
{
if (p != newProd && p != oldProd)
{
continue;
}
if (p == newProd)
{
newFirst = true;
}
break;
}
}
//Resolve based on first appearance
if (newFirst)
{
state.Action[key.ID] = newAction;
}
return;
}
else
{
throw new Exception($"Conflict in state {state} on entry {key}. Cannot resolve shift/shift conflict.");
}
}
}
state.Action[key.ID] = newAction;
}
