eachElement

Transfer corresponding elements of equal-size fixed arrays, optionally selecting a scalar field per element. Both endpoints use eachElement(); destinations require an aggregate return. Explicit zeroInitializeReturn clears unassigned scalar members; otherwise every scalar must be covered. A constant may instead initialize selected fields of a counted receiver/parameter array. The count is read once; only active elements are written, and zero or excessive counts perform no writes. Other fields remain. Compiler types provide the capacity, stride and field offsets. This preserves index correspondence.