Added a missing requires clause to the kkmeans object.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402367

dlib/svm/kkmeans.h

@@ -58,6 +58,15 @@ namespace dlib
             unsigned long i
         ) const
         {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(i < number_of_centers(),
+                "\tkcentroid kkmeans::get_kcentroid(i)"
+                << "\n\tYou have given an invalid value for i"
+                << "\n\ti:                   " << i 
+                << "\n\tnumber_of_centers(): " << number_of_centers() 
+                << "\n\tthis:                " << this
+                );
+
             return *centers[i];
         }
 

dlib/svm/kkmeans_abstract.h

@@ -65,6 +65,8 @@ namespace dlib
             unsigned long i
         ) const;
         /*!
+            requires
+                - i < number_of_centers()
             ensures
                 - returns a const reference to the ith kcentroid object contained in
                   this object.  Each kcentroid represents one of the centers found