public bool RecusiveDescent(BnfNonterminal t)
{
int rulesCount = t.RulesCount;
bool [] success = new bool [rulesCount];
int i = 0;
foreach (var rule in t.Rules)
{
int currentPosition = position;
success [i] = true;
foreach (var sym in rule.Parts)
{
if (sym.isTerminal == false)
{
if (RecusiveDescent(sym as BnfNonterminal) == false)
{
success [i] = false;
break;
}
}
else
{
int len = sym.Content.Length;
if (string.Compare(sym.Content, text.Substring(position, len)) == 0)
{
position += len;
continue;
}
else
{
success [i] = false;
break;
}
}
}
if (success [i] == false)
{
position = currentPosition;
}
i++;
}
int total = 0;
foreach (var b in success)
{
if (b)
{
total++;
}
}
if (total > 1)
{
throw new ApplicationException();
}
return(total == 1);
}
public static BnfGrammar Test1()
{
BnfNonterminal S = new BnfNonterminal(nameof(S));
BnfNonterminal A = new BnfNonterminal(nameof(A));
Symbol a = new Symbol(nameof(a));
Symbol b = new Symbol(nameof(b));
Symbol c = new Symbol(nameof(c));
Symbol d = new Symbol(nameof(d));
var rule1 = new BnfRule(S, new Symbol [] { c, A, d });
var rule2 = new BnfRule(A, new Symbol [] { a, b });
var rule3 = new BnfRule(A, new Symbol [] { a });
var G = new BnfGrammar();
G.Add(rule1);
G.Add(rule2);
G.Add(rule3);
return(G);
}
public BnfRule(BnfNonterminal nt, Symbol [] symbols_of_rule)
{
nonterminal = nt;
parts = symbols_of_rule;
}
