1 files changed, 16 insertions, 6 deletions
diff --git a/decoder/nt_span.h b/decoder/nt_span.h
index 46234b07..a918f301 100755
--- a/decoder/nt_span.h
+++ b/decoder/nt_span.h
@@ -8,10 +8,15 @@
 struct Span {
   int l,r;
   Span() : l(-1) {  }
+  bool is_null() const { return l<0; }
+  void print(std::ostream &o,char const* for_null="") const {
+    if (is_null())
+      o<<for_null;
+    else
+      o<<'<'<<l<<','<<r<<'>';
+  }
   friend inline std::ostream &operator<<(std::ostream &o,Span const& s) {
-    if (s.l<0)
-      return o;
-    return o<<'<'<<s.l<<','<<s.r<<'>';
+    s.print(o);return o;
   }
 };
 
@@ -20,10 +25,15 @@ struct NTSpan {
   WordID nt; // awkward: this is a positive index, used in TD.  but represented as negative in mixed terminal/NT space in rules/hgs.
   NTSpan() : nt(0) {  }
   // prints as possibly empty name (whatever you set of nt,s will show)
+  void print(std::ostream &o,char const* for_span_null="_",char const* for_null="") const {
+    if (nt>0) {
+      o<<TD::Convert(nt);
+      s.print(o,for_span_null);
+    } else
+      s.print(o,for_null);
+  }
   friend inline std::ostream &operator<<(std::ostream &o,NTSpan const& t) {
-    if (t.nt>0)
-      o<<TD::Convert(t.nt);
-    return o << t.s;
+    t.print(o);return o;
   }
 };