void head_finder::operator()(internal_node& inode)
{
// recurse, as we need the head annotations of all child nodes first
inode.each_child([&](node* child)
{
child->accept(*this);
});
if (rules_.find(inode.category()) == rules_.end())
LOG(fatal) << "No rule found for category " << inode.category()
<< " in rule table" << ENDLG;
// run the head finder for the syntactic category of the current node
auto idx = rules_.at(inode.category())->find_head(inode);
inode.head(inode.child(idx));
if (idx < 2)
return;
static auto is_punctuation = [](const class_label& cat)
{
static std::unordered_set<class_label> punctuation = {
"''"_cl, "``"_cl, "-LRB-"_cl, "-RRB-"_cl, "."_cl, ":"_cl, ";"_cl};
return punctuation.find(cat) != punctuation.end();
};
// clean up stage for handling coordinating clauses
if (inode.child(idx - 1)->category() == "CC"_cl
|| inode.child(idx - 1)->category() == "CONJP"_cl)
{
for (uint64_t i = 0; i <= idx - 2; ++i)
{
auto nidx = idx - 2 - i;
auto child = inode.child(nidx);
if (child->is_leaf() || !is_punctuation(child->category()))
{
inode.head(child);
return;
}
}
}
}
std::unique_ptr<node> binarizer::operator()(const internal_node& in)
{
auto res = make_unique<internal_node>(in.category());
if (in.num_children() <= 2)
{
in.each_child([&](const node* child)
{
res->add_child(child->accept(*this));
if (child == in.head_constituent())
res->head(res->child(res->num_children() - 1));
});
return std::move(res);
}
auto bin_lbl = class_label{static_cast<std::string>(in.category()) + "*"};
// locate head node
auto head = in.head_constituent();
if (!head)
throw exception{"Head constituent not labeled"};
uint64_t head_idx = 0;
for (uint64_t idx = 0; idx < in.num_children(); ++idx)
{
if (in.child(idx) == in.head_constituent())
head_idx = idx;
}
// eat left nodes
auto curr = res.get();
for (uint64_t idx = 0; idx < head_idx; ++idx)
{
curr->add_child(in.child(idx)->accept(*this));
// special case: if the head is the very last node, just add the
// remaining child (the head) to the current node
if (idx + 1 == head_idx && head_idx == in.num_children() - 1)
{
curr->add_child(in.child(idx + 1)->accept(*this));
curr->head(curr->child(1));
break;
}
else
{
auto bin = make_unique<internal_node>(bin_lbl);
auto next = bin.get();
curr->add_child(std::move(bin));
curr->head(curr->child(1));
curr = next;
}
}
// eat right nodes
for (uint64_t ridx = in.num_children() - 1; ridx > head_idx; --ridx)
{
// if the head is the next node, just add it and the current child
if (head_idx + 1 == ridx)
{
curr->add_child(in.child(ridx - 1)->accept(*this));
curr->head(curr->child(0));
curr->add_child(in.child(ridx)->accept(*this));
break;
}
else
{
auto bin = make_unique<internal_node>(bin_lbl);
auto next = bin.get();
curr->add_child(std::move(bin));
curr->head(curr->child(0));
curr->add_child(in.child(ridx)->accept(*this));
curr = next;
}
}
lexicon_populator pop;
res->accept(pop);
return std::move(res);
}