Section
std::mdspan
std::mdspan is a multidimensional array view that maps a multidimensional index to an element of the array. The mapping and element access policies are configurable, and the underlying array need not be contiguous or even exist in memory at all.
# Declarations
template<
class T,
class Extents,
class LayoutPolicy = std::layout_right,
class AccessorPolicy = std::default_accessor<T>
> class mdspan;
(since C++23)
# Notes
Feature-test macro Value Std Feature __cpp_lib_mdspan 202207L (C++23) std::mdspan __cpp_lib_submdspan 202306L (C++26) std::submdspan 202403L (C++26) std::mdspan padded layouts __cpp_lib_aligned_accessor 202411L (C++26) std::aligned_accessor
# Example
#include <cstddef>
#include <mdspan>
#include <print>
#include <vector>
int main()
{
std::vector v{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
// View data as contiguous memory representing 2 rows of 6 ints each
auto ms2 = std::mdspan(v.data(), 2, 6);
// View the same data as a 3D array 2 x 3 x 2
auto ms3 = std::mdspan(v.data(), 2, 3, 2);
// Write data using 2D view
for (std::size_t i = 0; i != ms2.extent(0); i++)
for (std::size_t j = 0; j != ms2.extent(1); j++)
ms2[i, j] = i * 1000 + j;
// Read back using 3D view
for (std::size_t i = 0; i != ms3.extent(0); i++)
{
std::println("slice @ i = {}", i);
for (std::size_t j = 0; j != ms3.extent(1); j++)
{
for (std::size_t k = 0; k != ms3.extent(2); k++)
std::print("{} ", ms3[i, j, k]);
std::println("");
}
}
}