1 files changed, 109 insertions, 3 deletions

diff --git a/decoder/tree_fragment.h b/decoder/tree_fragment.h
index f1c4c106..4a704bc4 100644
--- a/decoder/tree_fragment.h
+++ b/decoder/tree_fragment.h
@@ -11,6 +11,7 @@
 namespace cdec {
 
 class BreadthFirstIterator;
+class DepthFirstIterator;
 
 static const unsigned LHS_BIT         = 0x10000000u;
 static const unsigned RHS_BIT         = 0x20000000u;
@@ -53,16 +54,21 @@ class TreeFragment {
   // (S (NP a (X b) c d) (VP (V foo) (NP (NN bar))))
   explicit TreeFragment(const std::string& tree, bool allow_frontier_sites = false);
   void DebugRec(unsigned cur, std::ostream* out) const;
-  typedef BreadthFirstIterator iterator;
+  typedef DepthFirstIterator iterator;
   typedef ptrdiff_t difference_type;
   typedef unsigned value_type;
   typedef const unsigned * pointer;
   typedef const unsigned & reference;
 
+  // default iterator is DFS
   iterator begin() const;
   iterator begin(unsigned node_idx) const;
   iterator end() const;
 
+  BreadthFirstIterator bfs_begin() const;
+  BreadthFirstIterator bfs_begin(unsigned node_idx) const;
+  BreadthFirstIterator bfs_end() const;
+
  private:
   // cp is the character index in the tree
   // np keeps track of the nodes (nonterminals) that have been built
@@ -78,14 +84,106 @@ class TreeFragment {
 
 struct TFIState {
   TFIState() : node(), rhspos(), state() {}
-  TFIState(unsigned n, unsigned p, unsigned s) : node(n), rhspos(p), state(s) {}
+  TFIState(unsigned n, int p, unsigned s) : node(n), rhspos(p), state(s) {}
   bool operator==(const TFIState& o) const { return node == o.node && rhspos == o.rhspos && state == o.state; }
   bool operator!=(const TFIState& o) const { return node != o.node || rhspos != o.rhspos || state != o.state; }
   unsigned short node;
-  unsigned short rhspos;
+  short rhspos;
   unsigned char state;
 };
 
+class DepthFirstIterator : public std::iterator<std::forward_iterator_tag, unsigned> {
+  const TreeFragment* tf_;
+  std::deque<TFIState> q_;
+  unsigned sym;
+ public:
+  DepthFirstIterator() : tf_(), sym() {}
+  // used for begin
+  explicit DepthFirstIterator(const TreeFragment* tf, unsigned node_idx) : tf_(tf) {
+    q_.push_back(TFIState(node_idx, -1, 0));
+    Stage();
+    q_.back().state++;
+  }
+  // used for end
+  explicit DepthFirstIterator(const TreeFragment* tf) : tf_(tf) {}
+  const unsigned& operator*() const { return sym; }
+  const unsigned* operator->() const { return &sym; }
+  bool operator==(const DepthFirstIterator& other) const {
+    return (tf_ == other.tf_) && (q_ == other.q_);
+  }
+  bool operator!=(const DepthFirstIterator& other) const {
+    return (tf_ != other.tf_) || (q_ != other.q_);
+  }
+  unsigned node_idx() const { return q_.front().node; }
+  const DepthFirstIterator& operator++() {
+    TFIState& s = q_.back();
+    if (s.state == 0) {
+      Stage();
+      s.state++;
+    } else if (s.state == 1) {
+      const unsigned len = tf_->nodes[s.node].rhs.size();
+      s.rhspos++;
+      if (s.rhspos >= len) {
+        q_.pop_back();
+        while (!q_.empty()) {
+          TFIState& s = q_.back();
+          const unsigned len = tf_->nodes[s.node].rhs.size();
+          s.rhspos++;
+          if (s.rhspos < len) break;
+          q_.pop_back();
+        }
+      }
+      Stage();
+    }
+    return *this;
+  }
+  DepthFirstIterator operator++(int) {
+    DepthFirstIterator res = *this;
+    ++(*this);
+    return res;
+  }
+  // tell iterator not to explore the subtree rooted at sym
+  // should only be called once per NT symbol encountered
+  const DepthFirstIterator& truncate() {
+    assert(IsRHS(sym));
+    sym &= ALL_MASK;
+    sym |= FRONTIER_BIT;
+    q_.pop_back();
+    return *this;
+  }
+  unsigned child_node() const {
+    assert(IsRHS(sym));
+    return q_.back().node;
+  }
+  DepthFirstIterator remainder() const {
+    assert(IsRHS(sym));
+    return DepthFirstIterator(tf_, q_.back());
+  }
+  bool at_end() const {
+    return q_.empty();
+  }
+ private:
+  void Stage() {
+    if (q_.empty()) return;
+    const TFIState& s = q_.back();
+    if (s.state == 0) {
+      sym = (tf_->nodes[s.node].lhs & ALL_MASK) | LHS_BIT;
+    } else if (s.state == 1) {
+      sym = tf_->nodes[s.node].rhs[s.rhspos];
+      if (IsRHS(sym)) {
+        q_.push_back(TFIState(sym & ALL_MASK, -1, 0));
+        sym = tf_->nodes[sym & ALL_MASK].lhs | RHS_BIT;
+      }
+    }
+  }
+
+  // used by remainder
+  DepthFirstIterator(const TreeFragment* tf, const TFIState& s) : tf_(tf) {
+    q_.push_back(s);
+    Stage();
+  }
+};
+
 class BreadthFirstIterator : public std::iterator<std::forward_iterator_tag, unsigned> {
   const TreeFragment* tf_;
   std::deque<TFIState> q_;
@@ -172,6 +270,14 @@ class BreadthFirstIterator : public std::iterator<std::forward_iterator_tag, uns
   }
 };
 
+inline TreeFragment::iterator TreeFragment::begin() const { return iterator(this, nodes.size() - 1); }
+inline TreeFragment::iterator TreeFragment::begin(unsigned node_idx) const { return iterator(this, node_idx); }
+inline TreeFragment::iterator TreeFragment::end() const { return iterator(this); }
+
+inline BreadthFirstIterator TreeFragment::bfs_begin() const { return BreadthFirstIterator(this, nodes.size() - 1); }
+inline BreadthFirstIterator TreeFragment::bfs_begin(unsigned node_idx) const { return BreadthFirstIterator(this, node_idx); }
+inline BreadthFirstIterator TreeFragment::bfs_end() const { return BreadthFirstIterator(this); }
+
 inline std::ostream& operator<<(std::ostream& os, const TreeFragment& x) {
   x.DebugRec(x.nodes.size() - 1, &os);
   return os;