public static LalrTable ComputeTable(GrammarProductionDatabase db)
{
var ctx = new LalrContext(db);
ctx.ComputeStates();
return(ctx.mTable);
}
private Dictionary <Symbol, LalrItemSet> InternalGoto(GrammarProductionDatabase db)
{
HashSet <Symbol> symbols = new HashSet <Symbol>();
//var closure = this.Closure(db);
var closure = this;
foreach (var item in closure)
{
if (item.AtEnd)
{
continue;
}
symbols.Add(item.CurrentSymbol);
}
Dictionary <Symbol, LalrItemSet> itemSets = new Dictionary <Symbol, LalrItemSet>();
foreach (var symb in symbols)
{
itemSets[symb] = closure.Goto(symb).Closure(db);
}
return(itemSets);
}
public HashSet <TerminalSymbol> GetNextLookaheads(GrammarProductionDatabase db)
{
if (ParsingPoint == (Production.Body.Count - 1))
{
return new HashSet <TerminalSymbol> {
Lookahead
}
}
;
return(SymbolString.Concat(Production.Body.Range(ParsingPoint + 1), Lookahead).FirstSet(db));
}
}
private HashSet <TerminalSymbol> InternalFirstSet(GrammarProductionDatabase db)
{
if (Count == 0)
{
return(new HashSet <TerminalSymbol>());
}
HashSet <TerminalSymbol> ts = new HashSet <TerminalSymbol>();
HashSet <NonterminalSymbol> analyzed = new HashSet <NonterminalSymbol>();
InternalFirstSet(ts, analyzed, db);
return(ts);
}
private LalrItemSet InternalClosure(GrammarProductionDatabase db)
{
HashSet <LalrItem> added = new HashSet <LalrItem>();
HashSet <LalrItem> toAdd = new HashSet <LalrItem>();
HashSet <LalrItem> next = new HashSet <LalrItem>();
toAdd.UnionWith(this);
while (toAdd.Count != 0)
{
next.Clear();
foreach (var item in toAdd)
{
if (item.AtEnd || !(item.CurrentSymbol is NonterminalSymbol))
{
continue;
}
var productions = db[item.CurrentSymbol as NonterminalSymbol];
var nextLookaheads = item.GetNextLookaheads(db);
foreach (var p in productions)
{
foreach (var la in nextLookaheads)
{
var newItem = new LalrItem(p, 0, la);
if (!added.Contains(newItem) && !toAdd.Contains(newItem))
{
next.Add(newItem);
}
}
}
}
added.UnionWith(toAdd);
toAdd.Clear();
toAdd.UnionWith(next);
}
added.UnionWith(toAdd);
added.UnionWith(next);
return(new LalrItemSet(added));
}
private LalrContext(GrammarProductionDatabase db)
{
this.mDatabase = db;
}
public LalrItemSet Closure(GrammarProductionDatabase db)
{
return(Memoize.Function(ClosureName, Tuple.Create(this, db), (arg) => arg.Item1.InternalClosure(arg.Item2)));
}
public Dictionary <Symbol, LalrItemSet> Goto(GrammarProductionDatabase db)
{
return(Memoize.Function(GotoName2, Tuple.Create(this, db), (arg) => arg.Item1.InternalGoto(arg.Item2)));
}
private void InternalFirstSet(HashSet <TerminalSymbol> ts, HashSet <NonterminalSymbol> analyzed, GrammarProductionDatabase db)
{
foreach (var item in this)
{
if (item is TerminalSymbol)
{
ts.Add(item as TerminalSymbol);
break;
}
else
{
if (analyzed.Contains(item as NonterminalSymbol))
{
if (!db.IsNullable(item as NonterminalSymbol))
{
break;
}
else
{
continue;
}
}
analyzed.Add(item as NonterminalSymbol);
var rules = db[item as NonterminalSymbol];
foreach (var prod in rules)
{
prod.Body.InternalFirstSet(ts, analyzed, db);
}
if (!db.IsNullable(item as NonterminalSymbol))
{
break;
}
}
}
}
public HashSet <TerminalSymbol> FirstSet(GrammarProductionDatabase db)
{
return(Memoize.Function(FirstSetName, Tuple.Create(this, db), (input) => input.Item1.InternalFirstSet(input.Item2)));
}