diff -r 8f1c317ebeb4 -r b79bcba43661 lemon/xy.h
--- a/lemon/xy.h	Tue Jul 26 13:15:13 2005 +0000
+++ b/lemon/xy.h	Tue Jul 26 14:31:29 2005 +0000
@@ -306,7 +306,7 @@
       }
   
       ///Increments a bounding box with a point
-      BoundingBox& operator +=(const xy<T>& u){
+      BoundingBox& add(const xy<T>& u){
         if (_empty){
           bottom_left=top_right=u;
           _empty = false;
@@ -320,17 +320,17 @@
         return *this;
       }
   
-      ///Sums a bounding box and a point
-      BoundingBox operator +(const xy<T>& u){
-        BoundingBox b = *this;
-        return b += u;
-      }
+//       ///Sums a bounding box and a point
+//       BoundingBox operator +(const xy<T>& u){
+//         BoundingBox b = *this;
+//         return b += u;
+//       }
 
       ///Increments a bounding box with an other bounding box
-      BoundingBox& operator +=(const BoundingBox &u){
+      BoundingBox& add(const BoundingBox &u){
         if ( !u.empty() ){
-          *this += u.bottomLeft();
-          *this += u.topRight();
+          this->add(u.bottomLeft());
+	  this->add(u.topRight());
         }
         return *this;
       }
@@ -338,7 +338,20 @@
       ///Sums two bounding boxes
       BoundingBox operator +(const BoundingBox& u){
         BoundingBox b = *this;
-        return b += u;
+        return b.add(u);
+      }
+
+
+      ///Intersection of two bounding boxes
+      BoundingBox operator &(const BoundingBox& u){
+        BoundingBox b;
+	b.bottom_left.x=std::max(this->bottom_left.x,u.bottom_left.x);
+	b.bottom_left.y=std::max(this->bottom_left.y,u.bottom_left.y);
+	b.top_right.x=std::min(this->top_right.x,u.top_right.x);
+	b.top_right.y=std::min(this->top_right.y,u.top_right.y);
+	b._empty = this->_empty || u._empty ||
+	  b.bottom_left.x>top_right.x && b.bottom_left.y>top_right.y;
+        return b;
       }
 
     };//class Boundingbox