public Matcher(FST fst)
{
_FST = fst;
}
public void Concatenate(FST rhs)
{
List <int> previouslyFinalStates = GetFinalStates();
if (previouslyFinalStates.Count == 0)
{
throw new Exception("Automaton does not have any final states");
}
if (!StateExists(_StartState))
{
throw new Exception("Automaton does not have a start state");
}
if (!rhs.StateExists(rhs._StartState))
{
throw new Exception("RHS Automaton does not have a start state");
}
bool lhsStartWasFinal = IsFinal(_StartState);
bool rhsStartWasFinal = rhs.IsFinal(rhs._StartState);
// the mapping from the state IDs of the RHS automaton. Key is the
// original RHS state ID, Value is the new state ID in the source automaton
Dictionary <int, int> stateMapping = new Dictionary <int, int>();
// all previously final states become non-final unless the RHS start state is final
if (!rhsStartWasFinal)
{
foreach (int pf in previouslyFinalStates)
{
SetFinal(pf, false);
}
}
// copy over the states
foreach (KeyValuePair <int, State> rhsState in rhs._States)
{
int newState = AddState();
stateMapping.Add(rhsState.Value.Id, newState);
// final states in the RHS automaton remain final
if (rhsState.Value.IsFinal)
{
SetFinal(newState, true);
}
}
// now that all states exist, copy over the RHS transitions
foreach (KeyValuePair <int, State> rhsState in rhs._States)
{
foreach (FSTTransition t in rhsState.Value.Transitions)
{
AddTransition(stateMapping[t.Source], stateMapping[t.Target],
new Label(t.Input), new Label(t.Output));
}
}
// next, link the two automatons.
// first, each transition which ends in a previously final state is
// copied into a transition to the previous start state of RHS
int newRhsStart = stateMapping[rhs._StartState];
foreach (KeyValuePair <int, State> lhsState in _States)
{
State testState = lhsState.Value;
List <FSTTransition> transitions = testState.Transitions;
// Take care with this iteration as the loop adds to the state's transitions
for (int transition = transitions.Count - 1; transition >= 0; --transition)
{
FSTTransition link = transitions[transition];
if (previouslyFinalStates.Contains(link.Target))
{
testState.AddTransition(newRhsStart, new Label(link.Input), new Label(link.Output));
}
}
}
if (lhsStartWasFinal)
{
// need to introduce an eps transition to the rhs start state
AddTransition(_StartState, newRhsStart,
new Label(Label.SpecialSymbolEpsilon),
new Label(Label.SpecialSymbolEpsilon));
}
Clean();
}