Fixed a compile time bug in the offset_kernel. Also fixed some

bugs in the sparse vector operations and added a few more new
operations as well.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402952

dlib/svm/kernel.h

@@ -370,7 +370,7 @@ namespace dlib
 
         offset_kernel(const T& k, const scalar_type& offset_
         ) : kernel(k), offset(offset_) {}
-        offset_kernel() : offset(0.01) {}
+        offset_kernel() : kernel(T()), offset(0.01) {}
         offset_kernel(
             const offset_kernel& k
         ) : kernel(k.kernel), offset(k.offset) {}

dlib/svm/sparse_vector.h

@@ -57,15 +57,28 @@ namespace dlib
             while (ai != a.end())
             {
                 sum += ai->second*ai->second;
+                ++ai;
             }
             while (bi != b.end())
             {
                 sum += bi->second*bi->second;
+                ++bi;
             }
 
             return sum;
         }
 
+    // ------------------------------------------------------------------------------------
+
+        template <typename T, typename U>
+        typename T::value_type::second_type distance (
+            const T& a,
+            const U& b
+        )
+        {
+            return std::sqrt(distance_squared(a,b));
+        }
+
     // ------------------------------------------------------------------------------------
 
         template <typename T, typename U>
@@ -113,10 +126,11 @@ namespace dlib
         {
             typedef typename T::value_type::second_type scalar_type;
 
-            typename T::const_iterator i = a.begin();
+            typename T::const_iterator i;
 
             scalar_type sum = 0;
-            while (i != a.end())
+
+            for (i = a.begin(); i != a.end(); ++i)
             {
                 sum += i->second * i->second;
             }
@@ -124,6 +138,16 @@ namespace dlib
             return sum;
         }
 
+    // ------------------------------------------------------------------------------------
+
+        template <typename T>
+        typename T::value_type::second_type length (
+            const T& a
+        )
+        {
+            return std::sqrt(length_squared(a));
+        }
+
     }
 
 // ----------------------------------------------------------------------------------------

dlib/svm/sparse_vector_abstract.h

@@ -47,6 +47,22 @@ namespace dlib
                   a and b
         !*/
 
+    // ----------------------------------------------------------------------------------------
+
+        template <typename T, typename U>
+        typename T::value_type::second_type distance (
+            const T& a,
+            const U& b
+        );
+        /*!
+            requires
+                - a is a sorted range of std::pair objects
+                - b is a sorted range of std::pair objects
+            ensures
+                - returns the distance between the vectors
+                  a and b.  (i.e. std::sqrt(distance_squared(a,b)))
+        !*/
+
     // ----------------------------------------------------------------------------------------
 
         template <typename T, typename U>
@@ -76,6 +92,20 @@ namespace dlib
                 - returns dot(a,a) 
         !*/
 
+    // ----------------------------------------------------------------------------------------
+
+        template <typename T>
+        typename T::value_type::second_type length (
+            const T& a
+        );
+        /*!
+            requires
+                - a is a sorted range of std::pair objects
+                - b is a sorted range of std::pair objects
+            ensures
+                - returns std::sqrt(length_squared(a,a))
+        !*/
+
     }
 
 // ----------------------------------------------------------------------------------------