public virtual IIntSet Complement(IIntSet set)
{
if (set == null)
{
return(this.Complement());
}
return(set.Subtract(this));
}
/** Add label uniquely and disjointly; intersection with
* another set or int/char forces breaking up the set(s).
*
* Example, if reachable list of labels is [a..z, {k,9}, 0..9],
* the disjoint list will be [{a..j,l..z}, k, 9, 0..8].
*
* As we add NFA configurations to a DFA state, we might as well track
* the set of all possible transition labels to make the DFA conversion
* more efficient. W/o the reachable labels, we'd need to check the
* whole vocabulary space (could be 0..\uFFFF)! The problem is that
* labels can be sets, which may overlap with int labels or other sets.
* As we need a deterministic set of transitions from any
* state in the DFA, we must make the reachable labels set disjoint.
* This operation amounts to finding the character classes for this
* DFA state whereas with tools like flex, that need to generate a
* homogeneous DFA, must compute char classes across all states.
* We are going to generate DFAs with heterogeneous states so we
* only care that the set of transitions out of a single state are
* unique. :)
*
* The idea for adding a new set, t, is to look for overlap with the
* elements of existing list s. Upon overlap, replace
* existing set s[i] with two new disjoint sets, s[i]-t and s[i]&t.
* (if s[i]-t is nil, don't add). The remainder is t-s[i], which is
* what you want to add to the set minus what was already there. The
* remainder must then be compared against the i+1..n elements in s
* looking for another collision. Each collision results in a smaller
* and smaller remainder. Stop when you run out of s elements or
* remainder goes to nil. If remainder is non nil when you run out of
* s elements, then add remainder to the end.
*
* Single element labels are treated as sets to make the code uniform.
*/
protected virtual void AddReachableLabel(Label label)
{
if (_reachableLabels == null)
{
_reachableLabels = new OrderedHashSet <Label>();
}
/*
* [email protected]("addReachableLabel to state "+dfa.decisionNumber+"."+stateNumber+": "+label.getSet().toString(dfa.nfa.grammar));
* [email protected]("start of add to state "+dfa.decisionNumber+"."+stateNumber+": " +
* "reachableLabels="+reachableLabels.toString());
*/
if (_reachableLabels.Contains(label))
{
// exact label present
return;
}
IIntSet t = label.Set;
IIntSet remainder = t; // remainder starts out as whole set to add
int n = _reachableLabels.Count; // only look at initial elements
// walk the existing list looking for the collision
for (int i = 0; i < n; i++)
{
Label rl = _reachableLabels[i];
/*
* [email protected]("comparing ["+i+"]: "+label.toString(dfa.nfa.grammar)+" & "+
* rl.toString(dfa.nfa.grammar)+"="+
* intersection.toString(dfa.nfa.grammar));
*/
if (!Label.Intersect(label, rl))
{
continue;
}
//[email protected](label+" collides with "+rl);
// For any (s_i, t) with s_i&t!=nil replace with (s_i-t, s_i&t)
// (ignoring s_i-t if nil; don't put in list)
// Replace existing s_i with intersection since we
// know that will always be a non nil character class
IIntSet s_i = rl.Set;
IIntSet intersection = s_i.And(t);
_reachableLabels[i] = new Label(intersection);
// Compute s_i-t to see what is in current set and not in incoming
IIntSet existingMinusNewElements = s_i.Subtract(t);
//[email protected](s_i+"-"+t+"="+existingMinusNewElements);
if (!existingMinusNewElements.IsNil)
{
// found a new character class, add to the end (doesn't affect
// outer loop duration due to n computation a priori.
Label newLabel = new Label(existingMinusNewElements);
_reachableLabels.Add(newLabel);
}
/*
* [email protected]("after collision, " +
* "reachableLabels="+reachableLabels.toString());
*/
// anything left to add to the reachableLabels?
remainder = t.Subtract(s_i);
if (remainder.IsNil)
{
break; // nothing left to add to set. done!
}
t = remainder;
}
if (!remainder.IsNil)
{
/*
* [email protected]("before add remainder to state "+dfa.decisionNumber+"."+stateNumber+": " +
* "reachableLabels="+reachableLabels.toString());
* [email protected]("remainder state "+dfa.decisionNumber+"."+stateNumber+": "+remainder.toString(dfa.nfa.grammar));
*/
Label newLabel = new Label(remainder);
_reachableLabels.Add(newLabel);
}
/*
* [email protected]("#END of add to state "+dfa.decisionNumber+"."+stateNumber+": " +
* "reachableLabels="+reachableLabels.toString());
*/
}
