private void MakeIsNullable()
{
var nullables = new HashSet <Symbol>();
var loop = true;
while (loop)
{
loop = false;
foreach (var rule in Nonterminals.Where(rule => !nullables.Contains(rule)))
{
foreach (var production in rule.Body)
{
var count = production.Count(symbol => !nullables.Contains(symbol));
if (count == 0)
{
loop = nullables.Add(production.Head);
break;
}
}
}
}
foreach (var nullable in nullables)
{
nullable.IsNullable = true;
}
}
public Nonterminal GetNonterminal(string name)
{
return(Nonterminals.Where(o => o.Name == name).FirstOrDefault());
}
