cpp/container/mdspan/operator at

Returns a reference to the $th$ element of the mdspan.

@1@ Equivalent to.
 * This overload participates in overload resolution only if:
 * is ,
 * is, and
 * is.


 * Let be . Then the behavior is undefined if  is not a multidimensional index in, i.e.,  is.

@2,3@ Let be a parameter pack such that  is, then the operator is equivalent to.
 * This overload participates in overload resolution only if:
 * is, and
 * is.

Return value
A reference to the element