public static AugmentedGrammar Augement(Grammar grammar)
{
var augmentedStartingSymbol = grammar.StartingSymbol + "`";
var augmentedNonterminals = new List <string>();
augmentedNonterminals.Add(augmentedStartingSymbol);
augmentedNonterminals.AddRange(grammar.Nonterminals);
var augmentedTerminals = new List <string>();
augmentedTerminals.AddRange(grammar.Terminals);
var augmentedSymbols = new List <string>();
augmentedSymbols.AddRange(augmentedNonterminals);
augmentedSymbols.AddRange(augmentedTerminals);
var augmentedProductions = new Dictionary <string, List <LR0Item> >();
augmentedProductions[augmentedStartingSymbol] = new List <LR0Item>()
{
new LR0Item(augmentedStartingSymbol, "." + grammar.StartingSymbol)
};
foreach (var productionPair in grammar.Productions)
{
var lhs = productionPair.Key;
var lr0Items = new List <LR0Item>();
productionPair.Value.ForEach(rhs =>
{
var item = new LR0Item(lhs, "." + rhs);
lr0Items.Add(item);
});
augmentedProductions[lhs] = lr0Items;
}
return(new AugmentedGrammar()
{
Nonterminals = augmentedNonterminals,
Terminals = augmentedTerminals,
Productions = augmentedProductions,
StartingSymbol = augmentedStartingSymbol,
AllSymbols = augmentedSymbols
});
}
public LR0Item MoveDot()
{
var dotIndex = GetDotIndex();
if (dotIndex == rhs.Length - 1)
{
return(this);
}
var rhsBuilder = new StringBuilder(rhs);
rhsBuilder[dotIndex] = rhsBuilder[dotIndex + 1];
rhsBuilder[dotIndex + 1] = '.';
var newLR0Item = new LR0Item(lhs, rhsBuilder.ToString());
return(newLR0Item);
}
