private Nonterminal Map(NonterminalExpr rule)
{
if (!Nonterminals.TryGetValue(rule, out var mapped))
{
mapped = new Nonterminal(rule.Name);
Nonterminals.Add(rule, mapped);
foreach (var chain in rule.Body)
{
var body = new List <Symbol>();
foreach (var symbol in chain)
{
switch (symbol)
{
case TerminalExpr terminal:
body.Add(Map(terminal));
break;
case NonterminalExpr nonterminal:
body.Add(Map(nonterminal));
break;
}
}
Productions.Add(new Production(mapped, body));
}
}
return(mapped);
}
public Grammar From(NonterminalExpr startSymbol)
{
return(new Grammar(Map(startSymbol), Productions));
}