void HwcmScorer::extractHeadWordChain(TreePointer tree, vector<string> & history, vector<map<string, int> > & hwc) {
if (tree->GetLength() > 0) {
string head = getHead(tree);
if (head.empty()) {
for (std::vector<TreePointer>::const_iterator it = tree->GetChildren().begin(); it != tree->GetChildren().end(); ++it) {
extractHeadWordChain(*it, history, hwc);
}
}
else {
vector<string> new_history(kHwcmOrder);
new_history[0] = head;
hwc[0][head]++;
for (size_t hist_idx = 0; hist_idx < kHwcmOrder-1; hist_idx++) {
if (!history[hist_idx].empty()) {
string chain = history[hist_idx] + " " + head;
hwc[hist_idx+1][chain]++;
if (hist_idx+2 < kHwcmOrder) {
new_history[hist_idx+1] = chain;
}
}
}
for (std::vector<TreePointer>::const_iterator it = tree->GetChildren().begin(); it != tree->GetChildren().end(); ++it) {
extractHeadWordChain(*it, new_history, hwc);
}
}
}
}
string HwcmScorer::getHead(TreePointer tree) {
// assumption (only true for dependency parse: each constituent has a preterminal label, and corresponding terminal is head)
// if constituent has multiple preterminals, first one is picked; if it has no preterminals, empty string is returned
for (std::vector<TreePointer>::const_iterator it = tree->GetChildren().begin(); it != tree->GetChildren().end(); ++it)
{
TreePointer child = *it;
if (child->GetLength() == 1 && child->GetChildren()[0]->IsTerminal()) {
return child->GetChildren()[0]->GetLabel();
}
}
return "";
}
