1 files changed, 48 insertions, 0 deletions
diff --git a/extractor/phrase_builder.cc b/extractor/phrase_builder.cc
new file mode 100644
index 00000000..9faee4be
--- /dev/null
+++ b/extractor/phrase_builder.cc
@@ -0,0 +1,48 @@
+#include "phrase_builder.h"
+
+#include "phrase.h"
+#include "vocabulary.h"
+
+namespace extractor {
+
+PhraseBuilder::PhraseBuilder(shared_ptr<Vocabulary> vocabulary) :
+    vocabulary(vocabulary) {}
+
+Phrase PhraseBuilder::Build(const vector<int>& symbols) {
+  Phrase phrase;
+  phrase.symbols = symbols;
+  for (size_t i = 0; i < symbols.size(); ++i) {
+    if (vocabulary->IsTerminal(symbols[i])) {
+      phrase.words.push_back(vocabulary->GetTerminalValue(symbols[i]));
+    } else {
+      phrase.var_pos.push_back(i);
+    }
+  }
+  return phrase;
+}
+
+Phrase PhraseBuilder::Extend(const Phrase& phrase, bool start_x, bool end_x) {
+  vector<int> symbols = phrase.Get();
+  int num_nonterminals = 0;
+  if (start_x) {
+    num_nonterminals = 1;
+    symbols.insert(symbols.begin(),
+        vocabulary->GetNonterminalIndex(num_nonterminals));
+  }
+
+  for (size_t i = start_x; i < symbols.size(); ++i) {
+    if (!vocabulary->IsTerminal(symbols[i])) {
+      ++num_nonterminals;
+      symbols[i] = vocabulary->GetNonterminalIndex(num_nonterminals);
+    }
+  }
+
+  if (end_x) {
+    ++num_nonterminals;
+    symbols.push_back(vocabulary->GetNonterminalIndex(num_nonterminals));
+  }
+
+  return Build(symbols);
+}
+
+} // namespace extractor