internal static Dictionary <int, TThis> ExtractGroups(Automaton <TSequence, TElement, TElementDistribution, TSequenceManipulator, TThis> automaton)
{
var order = ComputeTopologicalOrderAndGroupSubgraphs(automaton, out var subGraphs);
return(BuildSubautomata(automaton.States, order, subGraphs));
}
/// <summary>
/// Creates an automaton <c>f'(s) = sum_{tu=s} f(t)g(u)</c>, where <c>f(t)</c> is the current
/// automaton (in builder) and <c>g(u)</c> is the given automaton.
/// The resulting automaton is also known as the Cauchy product of two automata.
/// </summary>
public void Append(
Automaton <TSequence, TElement, TElementDistribution, TSequenceManipulator, TThis> automaton,
int group = 0,
bool avoidEpsilonTransitions = true)
{
var oldStateCount = this.states.Count;
foreach (var state in automaton.States)
{
var stateBuilder = this.AddState();
stateBuilder.SetEndWeight(state.EndWeight);
foreach (var transition in state.Transitions)
{
var updatedTransition = transition;
updatedTransition.DestinationStateIndex += oldStateCount;
if (group != 0)
{
updatedTransition.Group = group;
}
stateBuilder.AddTransition(updatedTransition);
}
}
var secondStartState = this[oldStateCount + automaton.Start.Index];
if (avoidEpsilonTransitions &&
(AllEndStatesHaveNoTransitions() || !automaton.Start.HasIncomingTransitions))
{
// Remove start state of appended automaton and copy all its transitions to previous end states
for (var i = 0; i < oldStateCount; ++i)
{
var endState = this[i];
if (!endState.CanEnd)
{
continue;
}
for (var iterator = secondStartState.TransitionIterator; iterator.Ok; iterator.Next())
{
var transition = iterator.Value;
if (group != 0)
{
transition.Group = group;
}
if (transition.DestinationStateIndex == secondStartState.Index)
{
transition.DestinationStateIndex = endState.Index;
}
else
{
transition.Weight *= endState.EndWeight;
}
endState.AddTransition(transition);
}
endState.SetEndWeight(endState.EndWeight * secondStartState.EndWeight);
}
this.RemoveState(secondStartState.Index);
}
else
{
// Just connect all end states with start state of appended automaton
for (var i = 0; i < oldStateCount; i++)
{
var state = this[i];
if (state.CanEnd)
{
state.AddEpsilonTransition(state.EndWeight, secondStartState.Index, group);
state.SetEndWeight(Weight.Zero);
}
}
}
bool AllEndStatesHaveNoTransitions()
{
for (var i = 0; i < oldStateCount; ++i)
{
var state = this.states[i];
if (!state.EndWeight.IsZero && state.FirstTransitionIndex != -1)
{
return(false);
}
}
return(true);
}
}
