Added some missing asserts and cleaned up some things

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402383

dlib/svm/svm.h

@@ -850,12 +850,24 @@ namespace dlib
             cache_size(200),
             eps(0.001)
         {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(0 < nu && nu <= 1,
+                "\tsvm_nu_trainer::svm_nu_trainer(kernel,nu)"
+                << "\n\t invalid inputs were given to this function"
+                << "\n\t nu: " << nu 
+                );
         }
 
         void set_cache_size (
             long cache_size_
         )
         {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(cache_size_ > 0,
+                "\tvoid svm_nu_trainer::set_cache_size(cache_size_)"
+                << "\n\t invalid inputs were given to this function"
+                << "\n\t cache_size: " << cache_size_ 
+                );
             cache_size = cache_size_;
         }
 
@@ -869,6 +881,12 @@ namespace dlib
             scalar_type eps_
         )
         {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(eps_ > 0,
+                "\tvoid svm_nu_trainer::set_epsilon(eps_)"
+                << "\n\t invalid inputs were given to this function"
+                << "\n\t eps: " << eps_ 
+                );
             eps = eps_;
         }
 
@@ -895,6 +913,12 @@ namespace dlib
             scalar_type nu_
         )
         {
+            // make sure requires clause is not broken
+            DLIB_ASSERT(0 < nu_ && nu_ <= 1,
+                "\tvoid svm_nu_trainer::set_nu(nu_)"
+                << "\n\t invalid inputs were given to this function"
+                << "\n\t nu: " << nu_ 
+                );
             nu = nu_;
         }
 
@@ -1387,6 +1411,14 @@ namespace dlib
         scalar_type eps;
     }; // end of class svm_nu_trainer
 
+// ----------------------------------------------------------------------------------------
+
+    template <typename K>
+    void swap (
+        svm_nu_trainer<K>& a,
+        svm_nu_trainer<K>& b
+    ) { a.swap(b); }
+
 // ----------------------------------------------------------------------------------------
 
 }

dlib/svm/svm_abstract.h

@@ -157,9 +157,9 @@ namespace dlib
             ensures
                 - returns the number of megabytes of cache this object will use
                   when it performs training via the this->train() function.
-                  (bigger values of this may make training go faster but doesn't affect 
+                  (bigger values of this may make training go faster but won't affect 
                   the result.  However, too big a value will cause you to run out of 
-                  memory obviously.)
+                  memory, obviously.)
         !*/
 
         void set_epsilon (
@@ -252,6 +252,15 @@ namespace dlib
         !*/
     }; 
 
+    template <typename K>
+    void swap (
+        svm_nu_trainer<K>& a,
+        svm_nu_trainer<K>& b
+    ) { a.swap(b); }
+    /*!
+        provides a global swap
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     template <