public Production(Nonterminal head, IEnumerable <Symbol> tail)
{
Head = head ?? throw new ArgumentNullException(nameof(head));
var rhs = (tail ?? Enumerable.Empty <Symbol>()).ToArray();
if (rhs.Length > 1 && rhs.Any(symbol => symbol.IsEpsilon))
{
throw new ArgumentException($"{Symbol.Epsilon}-productions cannot have more than one symbol.");
}
if (rhs.Length == 0 || rhs.Length == 1 && rhs[0].IsEpsilon)
{
Tail = Array.Empty <Symbol>();
}
else
{
Tail = rhs;
}
}
public Grammar(
SymbolCache <TTokenKind, Terminal <TTokenKind> > terminals,
SymbolCache <TNonterminal, Nonterminal> nonterminals,
Nonterminal startSymbol,
IEnumerable <Production> productions,
Func <Grammar <TTokenKind, TNonterminal>, IFollowSymbolsAnalyzer <TTokenKind> > analyzerFactory)
{
if (productions == null)
{
throw new ArgumentNullException(nameof(productions));
}
StartSymbol = startSymbol ?? throw new ArgumentNullException(nameof(startSymbol));
Nonterminals = nonterminals ?? throw new ArgumentNullException(nameof(nonterminals));
Terminals = terminals ?? throw new ArgumentNullException(nameof(terminals));
// Productions are numbered 0,1,2,...,^Productions.Count
var prods = new List <Production>();
// Variables (productions on the shorter form (A -> α | β | ...) are numbered 0,1,...,^Variables.Count
var productionMap = Nonterminals.ToDictionary(symbol => symbol, _ => new List <(int, Production)>());
int index = 0;
foreach (var production in productions)
{
prods.Add(production);
productionMap[production.Head].Add((index, production));
index += 1;
}
ProductionsFor = productionMap.ToImmutableDictionary(kvp => kvp.Key,
kvp => (IReadOnlyList <(int, Production)>)kvp.Value);
if (prods.Count == 0)
{
throw new ArgumentException("The productions are empty.", nameof(productions));
}
Productions = prods;
// Calculate lookahead sets (Erasable, First, Follow) using strategy provided by the caller
_analyzer = analyzerFactory(this);
}
internal LrGotoEntry(int sourceState, Nonterminal nonterminalSymbol, int targetState)
{
SourceState = sourceState;
NonterminalSymbol = nonterminalSymbol;
TargetState = targetState;
}
