/** Optimize an alternative (list of grammar elements).
*
* Walk the chain of elements (which can be complicated loop blocks...)
* and throw away any epsilon transitions used to link up simple elements.
*
* This only removes 195 states from the java.g's NFA, but every little
* bit helps. Perhaps I can improve in the future.
*/
public virtual void OptimizeAlternative(StateCluster alt)
{
NFAState s = alt.left;
while (s != alt.right)
{
// if it's a block element, jump over it and continue
if (s.endOfBlockStateNumber != State.INVALID_STATE_NUMBER)
{
s = nfa.GetState(s.endOfBlockStateNumber);
continue;
}
Transition t = s.transition[0];
if (t is RuleClosureTransition)
{
s = ((RuleClosureTransition)t).followState;
continue;
}
if (t.label.IsEpsilon && !t.label.IsAction && s.NumberOfTransitions == 1)
{
// bypass epsilon transition and point to what the epsilon's
// target points to unless that epsilon transition points to
// a block or loop etc.. Also don't collapse epsilons that
// point at the last node of the alt. Don't collapse action edges
NFAState epsilonTarget = (NFAState)t.target;
if (epsilonTarget.endOfBlockStateNumber == State.INVALID_STATE_NUMBER &&
epsilonTarget.transition[0] != null)
{
s.SetTransition0(epsilonTarget.transition[0]);
//System.Console.Out.WriteLine( "### opt " + s.stateNumber + "->" + epsilonTarget.transition[0].target.stateNumber );
}
}
s = (NFAState)t.target;
}
}