private void breakRuleForNonnullableGrammar(Rule r, Grammar g, out List<Nonterminal> firstVanishing, out List<Symbol> rest)
{
firstVanishing = new List<Nonterminal>();
rest = new List<Symbol>();
foreach (Symbol s in r.Right)
{
if (rest.Count > 0)
rest.Add(s);
else
if (g.isVanishingSymbol(s))
firstVanishing.Add((Nonterminal)s);
else
rest.Add(s);
}
}
private List<Rule> buildRulesForNonnullableGrammar(Grammar g)
{
List<Rule> rules = new List<Rule>();
List<Rule> newRules = new List<Rule>();
foreach (Rule r in g.Rules)
{
if (r.isERule())
rules.Add(r);
else
{
newRules.Clear();
List<Nonterminal> firstVanishing;
List<Symbol> rest;
breakRuleForNonnullableGrammar(r, g, out firstVanishing, out rest);
if (firstVanishing.Count > 0)
newRules.AddRange(createNewRulesForFisrtVanishing(r, firstVanishing, rest));
if (rest.Count > 0)
newRules.Add(createRuleWithNoFisrtVanishing(r, rest));
if (g.isVanishingSymbol(r.Left))
newRules.AddRange(createRulesForLeftVanishing(newRules, r.Left));
rules.AddRange(newRules);
}
}
return rules;
}
private Nonterminal distinguishedSymbolForNonnullableGrammar(Grammar g)
{
Nonterminal S;
if (g.isVanishingSymbol(g.DistinguishedSymbol))
S = _nonnullableNonterminalsMap[g.DistinguishedSymbol.Sym];
else
S = g.DistinguishedSymbol;
return S;
}