public ContextFreeGrammar(string[] nonterminals, string[] terminals,
ProductionInfo[] rules, string starting)
{
if (HasDuplicates(nonterminals))
{
throw new ArgumentException("Nonterminal symbols cannot contain duplicates.");
}
if (HasDuplicates(terminals))
{
throw new ArgumentException("Terminal symbols cannot contain duplicates.");
}
if (HasDuplicates(rules))
{
throw new ArgumentException("Rules cannot contain duplicates.");
}
bool overlap = terminals.Intersect(nonterminals).Any();
if (overlap)
{
throw new ArgumentException("Terminal symbols and nonterminal symbols are not disjoint.");
}
var symbolByString = new Dictionary <string, GrammarSymbol>(nonterminals.Length + terminals.Length);
this.nonterminals = new GrammarSymbol[nonterminals.Length];
for (int i = 0; i < nonterminals.Length; i++)
{
this.nonterminals[i] = new GrammarSymbol(nonterminals[i], false);
symbolByString.Add(nonterminals[i], this.nonterminals[i]);
}
this.terminals = new GrammarSymbol[terminals.Length];
for (int i = 0; i < terminals.Length; i++)
{
this.terminals[i] = new GrammarSymbol(terminals[i], true);
symbolByString.Add(terminals[i], this.terminals[i]);
}
this.alphabet = (this.nonterminals).Concat(this.terminals).ToArray();
int startingIndex = Array.IndexOf(nonterminals, starting);
if (startingIndex < 0)
{
throw new ArgumentException("Start symbol must be a nonterminal symbol.");
}
this.starting = this.nonterminals[startingIndex];
var ruleList = new List <Production>(rules.Length);
foreach (var rule in rules)
{
if (!IsValid(rule))
{
throw new ArgumentException("Production rule is invalid.");
}
GrammarSymbol original = symbolByString[rule.Original];
var sentenceSymbols = new List <GrammarSymbol>();
foreach (string s in rule.DirectDerivative)
{
sentenceSymbols.Add(symbolByString[s]);
}
Sentence sentence = new Sentence(sentenceSymbols.ToArray());
ruleList.Add(new Production(original, sentence));
}
this.rules = ruleList.ToArray();
}
