cpp/utility/variant/get if

@1@ Index-based non-throwing accessor: If is not a null pointer and, returns a pointer to the value stored in the variant pointed to by. Otherwise, returns a null pointer value. The call is ill-formed if is not a valid index in the variant. @2@ Type-based non-throwing accessor: Equivalent to with  being the zero-based index of  in. The call is ill-formed if is not a unique element of.

Return value
Pointer to the value stored in the pointed-to variant or null pointer on error.