/// <summary>
/// Closes this item to a set of items
/// </summary>
/// <param name="closure">The list to close</param>
/// <param name="map">The current helper map</param>
public override void CloseTo(List <Item> closure, Dictionary <Rule, Dictionary <int, List <Item> > > map)
{
// the item was of the form [Var -> alpha .] (reduction)
// nothing to do
if (Action == LRActionCode.Reduce)
{
return;
}
// Get the next symbol in the item
Symbol next = GetNextSymbol();
// Here the item is of the form [Var -> alpha . next beta]
// If the next symbol is not a variable : do nothing
// If the next symbol is a variable :
Variable nextVar = next as Variable;
if (nextVar == null)
{
return;
}
// Firsts is a copy of the Firsts set for beta (next choice)
// Firsts will contains symbols that may follow Next
// Firsts will therefore be the lookahead for child items
TerminalSet firsts = new TerminalSet(GetNextChoice().Firsts);
// If beta is nullifiable (contains ε) :
if (firsts.Contains(Epsilon.Instance))
{
// Remove ε
firsts.Remove(Epsilon.Instance);
// Add the item's lookaheads
firsts.AddRange(lookaheads);
}
// For each rule that has Next as a head variable :
foreach (Rule rule in nextVar.Rules)
{
if (!map.ContainsKey(rule))
{
map.Add(rule, new Dictionary <int, List <Item> >());
}
Dictionary <int, List <Item> > sub = map[rule];
if (sub.ContainsKey(0))
{
List <Item> previouses = sub[0];
ItemLALR1 previous = previouses[0] as ItemLALR1;
previous.Lookaheads.AddRange(firsts);
}
else
{
List <Item> items = new List <Item>();
sub.Add(0, items);
ItemLALR1 New = new ItemLALR1(rule, 0, firsts);
closure.Add(New);
items.Add(New);
}
}
}
private void RemoveTerminals(TerminalSet terms, params Terminal[] termsToRemove)
{
foreach (var termToRemove in termsToRemove)
{
if (terms.Contains(termToRemove))
{
terms.Remove(termToRemove);
}
}
}
private void RemoveTerminals(TerminalSet terms, params Terminal[] termsToRemove)
{
foreach(var termToRemove in termsToRemove)
if (terms.Contains(termToRemove)) terms.Remove(termToRemove);
}
/// <summary>
/// Closes this item to a set of items
/// </summary>
/// <param name="closure">The list to close</param>
/// <param name="map">The current helper map</param>
public override void CloseTo(List <Item> closure, Dictionary <Rule, Dictionary <int, List <Item> > > map)
{
// the item was of the form [Var -> alpha .] (reduction)
// nothing to do
if (Action == LRActionCode.Reduce)
{
return;
}
// Get the next symbol in the item
Symbol next = GetNextSymbol();
// Here the item is of the form [Var -> alpha . Next beta]
// If the next symbol is not a variable : do nothing
// If the next symbol is a variable :
Variable nextVar = next as Variable;
if (nextVar == null)
{
return;
}
// Firsts is a copy of the Firsts set for beta (next choice)
// Firsts will contains symbols that may follow Next
// Firsts will therefore be the lookahead for child items
TerminalSet firsts = new TerminalSet(GetNextChoice().Firsts);
// If beta is nullifiable (contains ε) :
if (firsts.Contains(Epsilon.Instance))
{
// Remove ε
firsts.Remove(Epsilon.Instance);
// Add the item's lookahead as possible symbol for firsts
firsts.Add(lookahead);
}
// For each rule that has Next as a head variable :
foreach (Rule rule in nextVar.Rules)
{
if (!map.ContainsKey(rule))
{
map.Add(rule, new Dictionary <int, List <Item> >());
}
Dictionary <int, List <Item> > sub = map[rule];
if (!sub.ContainsKey(0))
{
sub.Add(0, new List <Item>());
}
List <Item> previouses = sub[0];
// For each symbol in Firsts : create the child with this symbol as lookahead
foreach (Terminal first in firsts)
{
// Child item creation and unique insertion
int sid = first.ID;
bool found = false;
foreach (Item previous in previouses)
{
if (previous.Lookaheads[0].ID == sid)
{
found = true;
break;
}
}
if (!found)
{
ItemLR1 New = new ItemLR1(rule, 0, first);
closure.Add(New);
previouses.Add(New);
}
}
}
}
