Switched the sparse vectors all over to unsigned integral keys and changed

the definition of what is officially a sparse vector to say that unsigned
integral keys are required.  Having this requirement is nice because it creates
a simple correspondence between dense vector index values and sparse vector keys.
The previous sparse vector definition was just excessively generic.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403523

dlib/svm/kcentroid_overloads.h

@@ -916,7 +916,7 @@ namespace dlib
             else
             {
                 // first compute w = cscale*alpha*w
-                for (typename std::map<long,scalar_type>::iterator i = w.begin(); i != w.end(); ++i)
+                for (typename std::map<unsigned long,scalar_type>::iterator i = w.begin(); i != w.end(); ++i)
                 {
                     i->second *= cscale*alpha;
                 }
@@ -935,7 +935,7 @@ namespace dlib
 
         kernel_type kernel;
 
-        std::map<long,scalar_type> w;
+        std::map<unsigned long,scalar_type> w;
         scalar_type alpha;
 
 

dlib/svm/sparse_vector_abstract.h

@@ -16,7 +16,7 @@ namespace dlib
         In dlib, sparse vectors are represented using the container objects
         in the C++ STL.  In particular, a sparse vector is any container that 
         contains a sorted range of std::pair<key, scalar_value> objects where:
-            - key is any type that can serve as a unique index or identifier (e.g. unsigned long)
+            - key is an unsigned integral type 
             - scalar_value is float, double, or long double
 
         So examples of valid sparse vectors are:    

dlib/test/kcentroid.cpp

@@ -106,8 +106,8 @@ namespace
     template <typename K>
     double dist (
         const K& k,
-        std::map<long,double> a,
-        std::map<long,double> b
+        std::map<unsigned long,double> a,
+        std::map<unsigned long,double> b
     )
     /*!
         ensures
@@ -357,7 +357,7 @@ namespace
     )
     /*!
         requires
-            - kernel_type::sample_type == a std::map<long,double> 
+            - kernel_type::sample_type == a std::map<unsigned long,double> 
             - kernel_type == a kernel that just computes a dot product
               between its inputs.  I.e. a linear kernel
         ensures
@@ -536,7 +536,7 @@ namespace
     )
     /*!
         requires
-            - kernel_type::sample_type == a std::map<long,double> 
+            - kernel_type::sample_type == a std::map<unsigned long,double> 
             - kernel_type == a kernel that just computes a dot product
               between its inputs + some constant.  I.e. a linear kernel
               wrapped by offset_kernel
@@ -553,7 +553,7 @@ namespace
 
         sample_type temp, temp2, temp3;
 
-        std::map<long,double> val, val2;
+        std::map<unsigned long,double> val, val2;
 
         const double b = std::sqrt(k.offset);
 
@@ -674,10 +674,10 @@ namespace
             test_kcentroid_with_offset_linear_kernel<offset_kernel<linear_kernel<matrix<double,4,1> > > >();
             test_kcentroid_with_linear_kernel<unopt_linear_kernel<matrix<double,5,1> > >();
             test_kcentroid_with_offset_linear_kernel<offset_kernel<unopt_linear_kernel<matrix<double,4,1> > > >();
-            test_kcentroid_with_sparse_linear_kernel<sparse_linear_kernel<std::map<long,double> > >();
-            test_kcentroid_with_offset_sparse_linear_kernel<offset_kernel<sparse_linear_kernel<std::map<long,double> > > >();
-            test_kcentroid_with_sparse_linear_kernel<unopt_sparse_linear_kernel<std::map<long,double> > >();
-            test_kcentroid_with_offset_sparse_linear_kernel<offset_kernel<unopt_sparse_linear_kernel<std::map<long,double> > > >();
+            test_kcentroid_with_sparse_linear_kernel<sparse_linear_kernel<std::map<unsigned long,double> > >();
+            test_kcentroid_with_offset_sparse_linear_kernel<offset_kernel<sparse_linear_kernel<std::map<unsigned long,double> > > >();
+            test_kcentroid_with_sparse_linear_kernel<unopt_sparse_linear_kernel<std::map<unsigned long,double> > >();
+            test_kcentroid_with_offset_sparse_linear_kernel<offset_kernel<unopt_sparse_linear_kernel<std::map<unsigned long,double> > > >();
         }
     } a;