You can easily do composable tagged (by index type or even comp time strings) tuples in C++. The syntax is not pretty, but there is minimal to non-existent over

You can easily do composable tagged (by index type or even comp time strings) tuples in C++. The syntax is not pretty, but there is minimal to non-existent overhead. On the other hand, thanks to the loose "duck typed" nature of templates, you can write functions that act on a subset of the fields of a type (even type checking it with concepts) while preserving the type of the whole object.