#include <cstddef> /* needed for std::size_t */
#include <cstdio> /* needed for printf */
#include <cassert> /* needed for assert */

enum class StorageOrder {ColMajor, RowMajor};

struct Matrix {
   const char* name; /* for debugging purposes */
   const std::size_t m; /* number of rows */
   const std::size_t n; /* number of columns */
   const std::size_t incRow;
   const std::size_t incCol;
   double* data;

   Matrix(const char* name,
         std::size_t m, std::size_t n, StorageOrder order) :
	 name(name),
	 m(m), n(n),
	 incRow(order == StorageOrder::ColMajor? 1: n),
	 incCol(order == StorageOrder::RowMajor? 1: m),
	 data(new double[m*n]) {
      std::printf("constructing %s\n", name);
   }

   ~Matrix() {
      std::printf("destructing %s\n", name);
      delete[] data;
   }

   const double& operator()(std::size_t i, std::size_t j) const {
      assert(i < m && j < n);
      return data[i*incRow + j*incCol];
   }
   
   double& operator()(std::size_t i, std::size_t j) {
      assert(i < m && j < n);
      return data[i*incRow + j*incCol];
   }

   void init() {
      for (std::size_t i = 0; i < m; ++i) {
	 for (std::size_t j = 0; j < n; ++j) {
	    data[i*incRow + j*incCol] = j * n + i + 1;
	 }
      }
   }

   void print() {
      for (std::size_t i = 0; i < m; ++i) {
	 std::printf("  ");
	 for (std::size_t j = 0; j < n; ++j) {
	    std::printf(" %4.1lf", data[i*incRow + j*incCol]);
	 }
	 std::printf("\n");
      }
   }
};

Matrix A("A (global)", 7, 8, StorageOrder::ColMajor);

int main() {
   {
      Matrix B("B (local)", 7, 8, StorageOrder::ColMajor);
   }
   Matrix("temporary", 7, 8, StorageOrder::ColMajor);
   Matrix* m = new Matrix("on heap", 7, 8, StorageOrder::RowMajor);
   delete m;
}