Added the pointer_to_column_vector function.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403210

dlib/matrix/matrix_utilities.h

@@ -336,6 +336,39 @@ namespace dlib
         return exp(vector);
     }
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename T 
+        >
+    struct op_pointer_to_col_vect : has_nondestructive_aliasing 
+    {
+        const static long cost = 1;
+        const static long NR = 0;
+        const static long NC = 1;
+        typedef typename memory_manager<char>::kernel_1a mem_manager_type;
+        typedef T type;
+        static type apply (const T* val, long r, long )
+        { return val[r]; }
+    };
+
+    template <
+        typename T
+        >
+    const dynamic_matrix_scalar_unary_exp<const T*,op_pointer_to_col_vect<T> > pointer_to_column_vector (
+        const T* ptr,
+        long nr
+    )
+    {
+        DLIB_ASSERT(nr > 0 , 
+                    "\tconst matrix_exp pointer_to_column_vector(ptr, nr)"
+                    << "\n\t nr must be bigger than 0"
+                    << "\n\t nr: " << nr
+        );
+        typedef dynamic_matrix_scalar_unary_exp<const T*,op_pointer_to_col_vect<T> > exp;
+        return exp(nr,1,ptr);
+    }
+
 // ----------------------------------------------------------------------------------------
 
     struct op_trans 

dlib/matrix/matrix_utilities_abstract.h

@@ -363,6 +363,29 @@ namespace dlib
                       R(r, c) == array[r][c]
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename T
+        >
+    const matrix_exp pointer_to_column_vector (
+        const T* ptr,
+        long nr
+    );
+    /*!
+        requires
+            - nr > 0
+            - ptr == a pointer to at least nr T objects
+        ensures
+            - returns a matrix M such that:
+                - M.nr() == nr
+                - m.nc() == 1
+                - for all valid i:
+                  M(i) == ptr[i]
+            - Note that the returned matrix doesn't take "ownership" of
+              the pointer and thus will not delete or free it.
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     const matrix_exp reshape_to_column_vector (

dlib/test/matrix3.cpp

@@ -593,6 +593,21 @@ namespace
         }
 
 
+        {
+            std::vector<double> v(34, 8);
+            std::vector<double> v2(34, 9);
+
+            DLIB_TEST(pointer_to_column_vector(&v[0], v.size()) == vector_to_matrix(v));
+            DLIB_TEST(pointer_to_column_vector(&v2[0], v.size()) != vector_to_matrix(v));
+        }
+
+        {
+            std::vector<long> v(1, 3);
+            std::vector<long> v2(1, 2);
+
+            DLIB_TEST(pointer_to_column_vector(&v[0], v.size()) == vector_to_matrix(v));
+            DLIB_TEST(pointer_to_column_vector(&v2[0], v.size()) != vector_to_matrix(v));
+        }
 
     }