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bool getDivisor(const Term* term) const {
if (empty())
return false;
_walker->goToRoot();
_walker->stepDown();
while (true) {
while (_walker->getNode()->getExponent() <=
_handler->getExponent(term, _position + _walker->getLevel() - 1)) {
if (!_walker->canStepDown())
return true;
_walker->stepDown();
}
while (!_walker->canStepRight()) {
_walker->stepUp();
if (_walker->atRoot())
return false;
}
_walker->stepRight();
}
}
// mergeSubtree assumes the sub-trees are of equal height and
// non-empty. TODO: adjust for _threshold.
bool mergeSubtree(TreeWalker& toWalker, TreeWalker& fromWalker) {
if (!fromWalker.canStepDown())
return false;
bool changed = false;
int rootLevel = fromWalker.getLevel();
// The goto's in this method are unfortunate, but I have not found
// a good way to get rid of them.
stepDown:
fromWalker.stepDown();
if (toWalker.getNode()->getChild()->getExponent() >
fromWalker.getNode()->getExponent()) {
toWalker.insertUnder(fromWalker.getNode()->getExponent());
toWalker.stepDown();
copySubtree(toWalker, fromWalker);
changed = true;
goto moveOn;
}
toWalker.stepDown();
while (true) {
// Now toWalker's exponent <= fromWalker's exponent. Then we
// step toWalker right as long as this property is preserved.
while (toWalker.canStepRight() &&
toWalker.getNode()->getNext()->getExponent() <=
fromWalker.getNode()->getExponent())
toWalker.stepRight();
// If the exponents are equal then we need to merge the subtrees
// of the current positions.
if (toWalker.getNode()->getExponent() ==
fromWalker.getNode()->getExponent()) {
if (fromWalker.canStepDown())
goto stepDown;
} else {
ASSERT(toWalker.getNode()->getExponent() <
fromWalker.getNode()->getExponent());
// Due to the previous right-stepping of toWalker, we know that
// the correct place to insert the new subtree is immediately to
// the right of toWalker.
toWalker.insertRightOf(fromWalker.getNode()->getExponent());
toWalker.stepRight();
copySubtree(toWalker, fromWalker);
changed = true;
}
moveOn:
while (!fromWalker.canStepRight()) {
fromWalker.stepUp();
toWalker.stepUp();
if (fromWalker.getLevel() == rootLevel)
return changed;
}
fromWalker.stepRight();
}
}
void copySubtree(TreeWalker& toWalker, TreeWalker& fromWalker) {
if (!fromWalker.canStepDown())
return;
int rootLevel = fromWalker.getLevel();
while (true) {
while (fromWalker.canStepDown()) {
fromWalker.stepDown();
toWalker.insertUnder(fromWalker.getNode()->getExponent());
toWalker.stepDown();
}
while (!fromWalker.canStepRight()) {
fromWalker.stepUp();
toWalker.stepUp();
if (fromWalker.getLevel() == rootLevel)
return;
}
fromWalker.stepRight();
toWalker.insertRightOf(fromWalker.getNode()->getExponent());
toWalker.stepRight();
}
}
bool insertProjectionOf(const TermTree& tree, Exponent from, Exponent to) {
if (tree.empty())
return false;
ExternalTerm term(*_handler);
TreeWalker* toWalker = _walker;//(*this);
TreeWalker* fromWalker = tree._walker;//((TermTree&)tree);
toWalker->goToRoot();
fromWalker->goToRoot();
fromWalker->stepDown();
bool changed = false;
while (true) {
if (to < fromWalker->getNode()->getExponent())
break;
if (from <= fromWalker->getNode()->getExponent()) {
if (empty()) {
copySubtree(*toWalker, *fromWalker);
changed = true;
} else
changed |= mergeSubtree(*toWalker, *fromWalker);
}
if (!fromWalker->canStepRight())
break;
fromWalker->stepRight();
}
return changed;
}
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