public BuilderItem(int action, LR1Item lr1Item)
{
Action = action;
LR1Item = lr1Item;
}
/// <summary>
/// Calculates the states in the LALR table
/// </summary>
void CalculateLookAheads()
{
bool bChanged;
do
{
bChanged = false;
int nState = 0;
foreach (var statePropogations in _lalrPropogations)
{
bool bStateChanged = false;
foreach (int nLR1Item in _lalrStates[nState])
{
var lr1Item = _lr1Items[nLR1Item];
if (statePropogations.ContainsKey(lr1Item.LR0ItemID))
{
foreach (var lalrPropogation in statePropogations[lr1Item.LR0ItemID])
{
int nGoto = lalrPropogation.LR0TargetState;
var item = new LR1Item(lalrPropogation.LR0TargetItem, lr1Item.LookAhead);
if (_lalrStates[nGoto].Add(GetLR1ItemID(item)))
{
bChanged = true;
bStateChanged = true;
}
}
}
}
if (bStateChanged)
{
_lalrStates[nState] = LR1Closure(_lalrStates[nState]);
}
nState++;
}
}
while (bChanged);
}
/// <summary>
/// Initializes the propogation table, and initial state of the LALR table
/// </summary>
int InitLALRTables()
{
int nLR0State = 0;
for (var i = 0; i < _lr0States.Count; i++ )
{
_lalrStates.Add(new HashSet<int>());
}
foreach (var lr0Kernel in _lr0Kernels)
{
var j = new HashSet<int>();
foreach (int jLR0ItemID in lr0Kernel)
{
var lr1Item = new LR1Item(jLR0ItemID, -1);
int nLR1ItemID = GetLR1ItemID(lr1Item);
j.Add(nLR1ItemID);
}
var jPrime = LR1Closure(j);
foreach (int jpLR1ItemID in jPrime)
{
var lr1Item = _lr1Items[jpLR1ItemID];
var lr0Item = _lr0Items[lr1Item.LR0ItemID];
if ((lr1Item.LookAhead != -1) || (nLR0State == 0))
{
_lalrStates[nLR0State].Add(jpLR1ItemID);
}
if (lr0Item.Position < _productions[lr0Item.Production].Right.Length)
{
int nToken = _productions[lr0Item.Production].Right[lr0Item.Position];
var lr0Successor = new LR0Item(lr0Item.Production, lr0Item.Position + 1);
int nLR0Successor = GetLR0ItemID(lr0Successor);
int nSuccessorState = _lrGotos[nLR0State][nToken];
if (lr1Item.LookAhead == -1)
{
AddPropogation(nLR0State, lr1Item.LR0ItemID, nSuccessorState, nLR0Successor);
}
else
{
var lalrItem = new LR1Item( nLR0Successor, lr1Item.LookAhead);
int nLALRItemID = GetLR1ItemID(lalrItem);
_lalrStates[nSuccessorState].Add(nLALRItemID);
}
}
}
nLR0State++;
}
return _lalrStates.Count;
}
/// <summary>
/// takes a set of LR1 Items (LR0 items with lookaheads) and produces all of those LR1 items reachable by substitution
/// </summary>
HashSet<int> LR1Closure(IEnumerable<int> items)
{
var closed = new HashSet<int>();
var open = items.ToList();
while (open.Count > 0)
{
int nLR1Item = open[0];
open.RemoveAt(0);
LR1Item lr1Item = _lr1Items[nLR1Item];
LR0Item lr0Item = _lr0Items[lr1Item.LR0ItemID];
closed.Add(nLR1Item);
if (lr0Item.Position < _productions[lr0Item.Production].Right.Length)
{
int nToken = _productions[lr0Item.Production].Right[lr0Item.Position];
if (_nonterminals.Contains(nToken))
{
var argFirst = new List<int>();
for (int nIdx = lr0Item.Position + 1; nIdx < _productions[lr0Item.Production].Right.Length; nIdx++)
{
argFirst.Add(_productions[lr0Item.Production].Right[nIdx]);
}
var first = First(argFirst, lr1Item.LookAhead);
int nProduction = 0;
foreach (var production in _productions)
{
if (production.Left == nToken)
{
foreach (int nTokenFirst in first)
{
var newLR0Item = new LR0Item(nProduction, 0);
int nNewLR0ItemID = GetLR0ItemID(newLR0Item);
var newLR1Item = new LR1Item(nNewLR0ItemID, nTokenFirst);
int nNewLR1ItemID = GetLR1ItemID(newLR1Item);
if (!open.Contains(nNewLR1ItemID) && !closed.Contains(nNewLR1ItemID))
{
open.Add(nNewLR1ItemID);
}
}
}
nProduction++;
}
}
}
}
return closed;
}
/// <summary>
/// Gets the ID for a particular LR1 Item
/// </summary>
int GetLR1ItemID(LR1Item item)
{
int nItemID = 0;
foreach (LR1Item oItem in _lr1Items)
{
if (oItem.Equals(item))
{
return nItemID;
}
nItemID++;
}
_lr1Items.Add(item);
return nItemID;
}
public void DumpLR1Item(LR1Item lr1Item)
{
var item = _parser.LR0Items[lr1Item.LR0ItemID];
_builder.Append(_parser.Grammar.TokenCategories[_parser.Productions[item.Production].Left]);
_builder.Append(" ->");
int nPosition = 0;
for (; ; )
{
if (nPosition == item.Position)
{
_builder.Append(" *");
}
if (nPosition >= _parser.Productions[item.Production].Right.Length)
{
break;
}
int nToken = _parser.Productions[item.Production].Right[nPosition];
_builder.Append(" ").Append(_parser.Grammar.TokenCategories[nToken]);
nPosition++;
}
if (lr1Item.LookAhead == -1)
{
_builder.Append(", $");
}
else
{
_builder.Append(", ").Append(_parser.Grammar.TokenCategories[lr1Item.LookAhead]);
}
_builder.AppendLine();
}
