Added a length_squared() member to vector.

dlib/geometry/vector.h

@@ -345,6 +345,14 @@ namespace dlib
 
         // ---------------------------------------
 
+        double length_squared(
+        ) const 
+        { 
+            return (double)(x()*x() + y()*y() + z()*z()); 
+        }
+
+        // ---------------------------------------
+
         typename vc_rebind<double,3>::type normalize (
         ) const 
         {
@@ -697,6 +705,13 @@ namespace dlib
 
         // ---------------------------------------
 
+        double length_squared(
+        ) const 
+        { 
+            return (double)(x()*x() + y()*y()); 
+        }
+
+        // ---------------------------------------
 
         typename vc_rebind<double,2>::type normalize (
         ) const 

dlib/geometry/vector_abstract.h

@@ -152,6 +152,13 @@ namespace dlib
                 - returns the length of the vector
         !*/
 
+        double length_squared(
+        ) const;
+        /*!
+            ensures
+                - returns length()*length() 
+        !*/
+
         T& x (
         );
         /*!