public static bool Scan(this IDfaSimulation dfa, int[] input, out int action)
{
int state = dfa.Start;
int?acceptingState = null;
foreach (var item in input)
{
if (!dfa.TryNext(state, item, out state))
{
break;
}
if (dfa.IsAccepting(state))
{
acceptingState = state;
}
}
if (!acceptingState.HasValue)
{
action = -1;
return(false);
}
var optAction = dfa.GetAction(acceptingState.Value);
action = optAction.GetValueOrDefault(-1);
return(true);
}
public IReceiver <Msg> Accept(IReceiver <Msg> visitor)
{
int start = 0, pos = 0;
int length = text.Length;
while (pos != length)
{
int state = dfa.Start;
int?acceptingState = null;
// Find longest token
for (; pos != length; ++pos)
{
int item = text[pos];
if (!dfa.TryNext(state, item, out state))
{
break;
}
if (dfa.IsAccepting(state))
{
acceptingState = state;
}
}
// Fail
if (!acceptingState.HasValue)
{
throw new Exception("Unexpected character at pos " + pos);
}
int action = dfa.GetAction(acceptingState.Value) ?? -1;
int tokenLength = pos - start;
var production = descriptor.Matchers[action];
if (production.Outcome != null)
{
TokenFactoryDelegate tokenFactory = tokenFactories[action];
// Emit next token
visitor = visitor.Next(
new Msg(
production.Outcome.Index,
tokenFactory(text.Substring(start, tokenLength)),
new Loc(Loc.MemoryString, start, pos)));
}
start = pos;
}
return(visitor.Done());
}