added const overload for operator [] in matrix view, added stddef.h include,...

added const overload for operator [] in matrix view, added stddef.h include, renamed Proxy to Vectorview

src/matrix_view.h

@@ -3,6 +3,8 @@
 
 // Modified code from https://github.com/pwwiur/Matrix
 
+#include <stddef.h>
+
 template <typename T>
 class MatrixView
 {
@@ -10,10 +12,10 @@ private:
   T *arr;
   size_t numRows, numColumns;
 
-  class Proxy
+  class VectorView
   {
   public:
-    Proxy(T *arr, size_t columns, size_t x) : px_arr(arr), px_columns(columns), px_x(x) {}
+    VectorView(T *arr, size_t columns, size_t x) : px_arr(arr), px_columns(columns), px_x(x) {}
     T &
     operator[](size_t y)
     {
@@ -31,10 +33,15 @@ public:
     if (rows == 0 || columns == 0) throw "Matrix initialization arguments rows and columns must be greater than zero.";
   }
 
-  Proxy
+  VectorView
   operator[](size_t x)
   {
-    return Proxy(arr, numColumns, x);
+    return VectorView(arr, numColumns, x);
+  }
+  const VectorView
+  operator[](size_t x) const
+  {
+    return VectorView(arr, numColumns, x);
   }
 };