1 files changed, 11 insertions, 3 deletions
diff --git a/decoder/sparse_vector.h b/decoder/sparse_vector.h
index 6a8c9bf4..2b4a63a9 100644
--- a/decoder/sparse_vector.h
+++ b/decoder/sparse_vector.h
@@ -185,10 +185,15 @@ public:
     }
 
     std::ostream &operator<<(std::ostream &out) const {
+        bool first = true;
         for (typename std::map<int, T>::const_iterator 
-                it = _values.begin(); it != _values.end(); ++it)
-            out << (it == _values.begin() ? "" : ";")
-	        << FD::Convert(it->first) << '=' << it->second;
+                it = _values.begin(); it != _values.end(); ++it) {
+          // by definition feature id 0 is a dummy value
+          if (it->first == 0) continue;
+          out << (first ? "" : ";")
+	      << FD::Convert(it->first) << '=' << it->second;
+          first = false;
+        }
         return out;
     }
 
@@ -216,6 +221,9 @@ public:
     void clear() {
         _values.clear();
     }
+    void clear_value(int index) {
+      _values.erase(index);
+    }
 
     void swap(SparseVector<T>& other) {
       _values.swap(other._values);