// [Sec 4, ES2008]
private void BuildTree(Dictionary <SppfNode, SppfNode> nodes, HashSet <Item> processed, InteriorNode node, Item item)
{
processed.Add(item);
if (item.Production.Rhs.Count == 0)
{
var i = node.EndPosition;
var v = NewOrExistingNode(nodes, new SymbolNode(item.Production.Lhs, i, i));
//if there is no SPPF node v labeled (A, i, i)
//create one with child node ϵ
v.AddFamily(new Family(new EpsilonNode(i, i)));
// basically, SymbolNodes with no children have empty children
}
else if (item.CurrentPosition == 1)
{
var prevWord = item.PrevWord;
if (prevWord.IsTerminal)
{
var a = (Terminal)prevWord;
var i = node.EndPosition;
var v = NewOrExistingNode(nodes, new TerminalNode(a, i - 1, i));
node.AddFamily(new Family(v));
}
else
{
var C = (Nonterminal)prevWord;
var j = node.StartPosition;
var i = node.EndPosition;
var v = NewOrExistingNode(nodes, new SymbolNode(C, j, i));
node.AddFamily(new Family(v));
foreach (var reduction in item.Reductions)
{
if (reduction.Label != j)
{
continue;
}
var q = reduction.Item;
if (!processed.Contains(q))
{
BuildTree(nodes, processed, v, q);
}
}
}
}
else if (item.PrevWord.IsTerminal)
{
var a = (Terminal)item.PrevWord;
var j = node.StartPosition;
var i = node.EndPosition;
var v = NewOrExistingNode(nodes, new TerminalNode(a, i - 1, i));
var w = NewOrExistingNode(nodes, new IntermediateNode(item.Decrement(), j, i - 1));
foreach (var predecessor in item.Predecessors)
{
if (predecessor.Label != i - 1)
{
continue;
}
var pPrime = predecessor.Item;
if (!processed.Contains(pPrime))
{
BuildTree(nodes, processed, w, pPrime);
}
}
node.AddFamily(new Family(w, v));
}
else
{
var C = (Nonterminal)item.PrevWord;
foreach (var reduction in item.Reductions)
{
var l = reduction.Label;
var q = reduction.Item;
var j = node.StartPosition;
var i = node.EndPosition;
var v = NewOrExistingNode(nodes, new SymbolNode(C, l, i));
if (!processed.Contains(q))
{
BuildTree(nodes, processed, v, q);
}
var w = NewOrExistingNode(nodes, new IntermediateNode(item.Decrement(), j, l));
foreach (var predecessor in item.Predecessors)
{
if (predecessor.Label != l)
{
continue;
}
var pPrime = predecessor.Item;
if (!processed.Contains(pPrime))
{
BuildTree(nodes, processed, w, pPrime);
}
}
node.AddFamily(new Family(w, v));
}
}
}
