What is idiomatic modern C++ for algebraic data types?

Question

Suppose, for example, you want to implement a spreadsheet Cell in C++. A cell can be either a string, a number, or perhaps empty. Ignore other cases, like it being a formula.

In Haskell, you might do something like:

data Cell = CellStr String | CellDbl Double | None 

What is considered the current "best practice" for doing it in C++? Use a union in a structure with a type indicator, or something else?

Answer 1

struct empty_type {}; using cell_type = boost::variant<std::string, double, empty_type>; 

Then you would do something with the cell with:

boost::apply_visitor(some_visitor(), cell);