Made resizable_tensor construction and assignment from matrices automatically

set the size of the tensor.

dlib/dnn/tensor.h

@@ -267,6 +267,15 @@ namespace dlib
         )
         {}
 
+        template <typename EXP>
+        resizable_tensor(
+            const matrix_exp<EXP>& item
+        )
+        {
+            set_size(item.nr(), item.nc());
+            *this = item;
+        }
+
         explicit resizable_tensor(
             long n_, long k_ = 1, long nr_ = 1, long nc_ = 1
         ) 
@@ -319,12 +328,34 @@ namespace dlib
         }
 
         template <typename EXP>
-        resizable_tensor& operator= (const matrix_exp<EXP>& item)
+        resizable_tensor& operator= (
+            const matrix_exp<EXP>& item
+        )
         {
+            set_size(item.nr(), item.nc());
             tensor::operator=(item);
             return *this;
         }
 
+        template <typename EXP>
+        resizable_tensor& operator+= (
+            const matrix_exp<EXP>& item
+        )
+        {
+            set_size(item.nr(), item.nc());
+            tensor::operator+=(item);
+            return *this;
+        }
+
+        template <typename EXP>
+        resizable_tensor& operator-= (
+            const matrix_exp<EXP>& item
+        )
+        {
+            set_size(item.nr(), item.nc());
+            tensor::operator-=(item);
+            return *this;
+        }
 
         void set_size(
             long n_, long k_ = 1, long nr_ = 1, long nc_ = 1

dlib/dnn/tensor_abstract.h

@@ -412,6 +412,22 @@ namespace dlib
                 - #nc() == 0
         !*/
 
+        template <typename EXP>
+        resizable_tensor(
+            const matrix_exp<EXP>& item
+        );
+        /*!
+            requires
+                - item contains float values
+            ensures
+                - #num_samples() == item.nr()
+                - #k() == item.nc()
+                - #nr() == 1
+                - #nc() == 1
+                - Assigns item to *this tensor by performing:
+                  set_ptrm(host(), num_samples(), k()*nr()*nc()) = item;
+        !*/
+
         explicit resizable_tensor(
             long n_, long k_ = 1, long nr_ = 1, long nc_ = 1
         );
@@ -470,6 +486,54 @@ namespace dlib
                 - #nr() == nr_
                 - #nc() == nc_
         !*/
+
+        template <typename EXP>
+        resizable_tensor& operator= (
+            const matrix_exp<EXP>& item
+        );
+        /*!
+            requires
+                - item contains float values
+            ensures
+                - #num_samples() == item.nr()
+                - #k() == item.nc()
+                - #nr() == 1
+                - #nc() == 1
+                - Assigns item to *this tensor by performing:
+                  set_ptrm(host(), num_samples(), k()*nr()*nc()) = item;
+        !*/
+
+        template <typename EXP>
+        resizable_tensor& operator+= (
+            const matrix_exp<EXP>& item
+        );
+        /*!
+            requires
+                - item contains float values
+            ensures
+                - #num_samples() == item.nr()
+                - #k() == item.nc()
+                - #nr() == 1
+                - #nc() == 1
+                - Adds item to *this tensor by performing:
+                  set_ptrm(host(), num_samples(), k()*nr()*nc()) += item;
+        !*/
+
+        template <typename EXP>
+        resizable_tensor& operator-= (
+            const matrix_exp<EXP>& item
+        );
+        /*!
+            requires
+                - item contains float values
+            ensures
+                - #num_samples() == item.nr()
+                - #k() == item.nc()
+                - #nr() == 1
+                - #nc() == 1
+                - Subtracts item from *this tensor by performing:
+                  set_ptrm(host(), num_samples(), k()*nr()*nc()) -= item;
+        !*/
     };
 
     void serialize(const tensor& item, std::ostream& out);