/**
* /// Reverses an fst
* ///
* /// @param fst the fst to reverse
* /// @return the reversed fst
*/
public static Fst Get(Fst fst)
{
if (fst.Semiring == null)
{
return(null);
}
ExtendFinal.Apply(fst);
Semiring semiring = fst.Semiring;
Fst res = new Fst(fst.GetNumStates());
res.Semiring = semiring;
res.Isyms = fst.Osyms;
res.Osyms = fst.Isyms;
State[] stateMap = new State[fst.GetNumStates()];
int numStates = fst.GetNumStates();
for (int i = 0; i < numStates; i++)
{
State _is = fst.GetState(i);
State s = new State(semiring.Zero);
res.AddState(s);
stateMap[_is.GetId()] = s;
if (_is.FinalWeight != semiring.Zero)
{
res.SetStart(s);
}
}
stateMap[fst.Start.GetId()].FinalWeight = semiring.One;
for (int i = 0; i < numStates; i++)
{
State olds = fst.GetState(i);
State news = stateMap[olds.GetId()];
int numArcs = olds.GetNumArcs();
for (int j = 0; j < numArcs; j++)
{
Arc olda = olds.GetArc(j);
State next = stateMap[olda.NextState.GetId()];
Arc newa = new Arc(olda.Ilabel, olda.Olabel,
semiring.Reverse(olda.Weight), news);
next.AddArc(newa);
}
}
ExtendFinal.Undo(fst);
return(res);
}