Fixed some confusing bits of the vector spec and also

added a unary - operator.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402815

dlib/geometry/vector.h

@@ -522,6 +522,14 @@ namespace dlib
 
         // ---------------------------------------
 
+        vector operator - (
+        ) const
+        {
+            return vector(-x(), -y(), -z());
+        }
+
+        // ---------------------------------------
+
         vector operator - (
             const vector& rhs
         ) const
@@ -869,6 +877,14 @@ namespace dlib
 
         // ---------------------------------------
 
+        vector operator - (
+        ) const
+        {
+            return vector(-x(), -y());
+        }
+
+        // ---------------------------------------
+
         vector operator - (
             const vector& rhs
         ) const

dlib/geometry/vector_abstract.h

@@ -145,7 +145,7 @@ namespace dlib
         !*/
 
 
-        T length(
+        double length(
         ) const;
         /*!
             ensures
@@ -216,7 +216,7 @@ namespace dlib
                 - returns the result of the cross product between *this and rhs
         !*/
 
-        vector normalize (
+        vector<double,NR> normalize (
         ) const;
         /*!
             ensures
@@ -239,6 +239,13 @@ namespace dlib
                 - returns the result of subtracting rhs from *this
         !*/
 
+        vector operator- (
+        ) const;
+        /*!
+            ensures
+                - returns -1*(*this) 
+        !*/
+
         vector operator/ (
             const T rhs
         ) const;

dlib/test/geometry.cpp

@@ -38,6 +38,10 @@ namespace
         DLIB_CASSERT(p2.x() == 2,"");
         DLIB_CASSERT(p2.y() == 3,"");
 
+        DLIB_CASSERT((-p2).x() == -2,"");
+        DLIB_CASSERT((-p2).y() == -3,"");
+
+
         p2 += p2;
         DLIB_CASSERT(p2.x() == 4,"");
         DLIB_CASSERT(p2.y() == 6,"");
@@ -238,6 +242,13 @@ namespace
 
         }
 
+        {
+            dlib::vector<double> v(3,4,5);
+            DLIB_CASSERT((-v).x() == -3.0,"");
+            DLIB_CASSERT((-v).y() == -4.0,"");
+            DLIB_CASSERT((-v).z() == -5.0,"");
+        }
+
     }