Added some missing requires clauses and asserts

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402391

dlib/svm/kcentroid.h

@@ -43,6 +43,14 @@ namespace dlib
             my_tolerance(tolerance_),
             my_max_dictionary_size(max_dictionary_size_)
         {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(tolerance_ >= 0,
+                "\tkcentroid::kcentroid()"
+                << "\n\t You have to give a positive tolerance"
+                << "\n\t this: " << this
+                << "\n\t tolerance: " << tolerance_ 
+                );
+
             clear_dictionary();
         }
 

dlib/svm/kcentroid_abstract.h

@@ -55,6 +55,8 @@ namespace dlib
             unsigned long max_dictionary_size_ = 1000000
         );
         /*!
+            requires
+                - tolerance >= 0
             ensures
                 - this object is properly initialized
                 - #tolerance() == tolerance_

dlib/svm/krls.h

@@ -38,6 +38,14 @@ namespace dlib
             my_tolerance(tolerance_),
             my_max_dictionary_size(max_dictionary_size_)
         {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(tolerance_ >= 0,
+                "\tkrls::krls()"
+                << "\n\t You have to give a positive tolerance"
+                << "\n\t this: " << this
+                << "\n\t tolerance: " << tolerance_ 
+                );
+
             clear_dictionary();
         }
 

dlib/svm/krls_abstract.h

@@ -53,6 +53,8 @@ namespace dlib
             unsigned long max_dictionary_size_ = 1000000
         );
         /*!
+            requires
+                - tolerance >= 0
             ensures
                 - this object is properly initialized
                 - #tolerance() == tolerance_