public DFA <RegularLanguageState> BuildLanguage()
{
var transitionTableBuilder = new TransitionTableBuilder <RegularLanguageState>();
var acceptingStates = new HashSet <RegularLanguageState>();
var visited = new HashSet <RegularLanguageState>();
var toVisit = new HashSet <RegularLanguageState>();
var startState = traverser.GetFirstPos(root);
toVisit.Add(startState);
while (toVisit.Count > 0)
{
var state = toVisit.First();
toVisit.Remove(state);
visited.Add(state);
if (state.ContainsTerminalPosition())
{
acceptingStates.Add(state);
}
foreach (char group in state.GetPositionGroups())
{
var newState = new RegularLanguageState();
foreach (ConstantExpression pos in state.GetPositions(group))
{
newState.UnionWith(traverser.GetFollowPos(pos));
}
if (!newState.IsEmpty)
{
transitionTableBuilder.Add(
Edge.From(state).By(group).To(newState)
);
if (!visited.Contains(newState) && !toVisit.Contains(newState))
{
toVisit.Add(newState);
}
}
}
}
return(new DFA <RegularLanguageState>(startState,
visited,
acceptingStates, transitionTableBuilder.Build()));
}
private void DFS(Expression start)
{
foreach (Expression expr in start)
{
DFS(expr);
}
if (start is TerminalExpression)
{
var newState = new RegularLanguageState(true);
firstPos[start] = newState;
lastPos[start] = newState;
nullable[start] = false;
}
else if (start is ConstantExpression)
{
var newState = new RegularLanguageState();
newState.AddPosition((ConstantExpression)start);
firstPos[start] = newState;
lastPos[start] = newState;
nullable[start] = false;
}
else if (start is ConcatenationExpression)
{
var ce = (ConcatenationExpression)start;
bool leftIsNullable = nullable[ce.Left];
bool rightIsNullable = nullable[ce.Right];
if (leftIsNullable)
{
firstPos[start] = RegularLanguageState.Union(firstPos[ce.Left], firstPos[ce.Right]);
}
else
{
firstPos[start] = firstPos[ce.Left];
}
if (rightIsNullable)
{
lastPos[start] = RegularLanguageState.Union(lastPos[ce.Left], lastPos[ce.Right]);
}
else
{
lastPos[start] = lastPos[ce.Right];
}
nullable[start] = leftIsNullable && rightIsNullable;
var leftLastPos = lastPos[ce.Left];
var rightFirstPos = firstPos[ce.Right];
foreach (char group in leftLastPos.GetPositionGroups())
{
foreach (ConstantExpression position in leftLastPos.GetPositions(group))
{
GetFollowPos(position).UnionWith(rightFirstPos);
}
}
}
else if (start is AlternationExpression)
{
var ce = (AlternationExpression)start;
firstPos[start] = RegularLanguageState.Union(firstPos[ce.Left], firstPos[ce.Right]);
lastPos[start] = RegularLanguageState.Union(lastPos[ce.Left], lastPos[ce.Right]);
nullable[start] = nullable[ce.Left] || nullable[ce.Right];
}
else if (start is IterationExpression)
{
var ce = (IterationExpression)start;
firstPos[start] = firstPos[ce.Inner];
lastPos[start] = lastPos[ce.Inner];
nullable[start] = true;
var leftLastPos = lastPos[ce.Inner];
var rightFirstPos = firstPos[ce.Inner];
foreach (char group in leftLastPos.GetPositionGroups())
{
foreach (ConstantExpression position in leftLastPos.GetPositions(group))
{
GetFollowPos(position).UnionWith(rightFirstPos);
}
}
}
}
