Modern C++ Programming Cookbook

How it works...

std::variant is a class template that models a type-safe union, holding a value of one of its possible alternatives at any given time. In some rare cases, it is possible, though, that a variant object does not store any value. std::variant has a member function called valueless_by_exception() that returns true if the variant does not hold a value, which is possible only in case of an exception during initialization, therefore, the name of the function.

The size of an std::variant object is as large as its largest alternative. A variant does not store additional data. The value stored by the variant is allocated within the memory representation of the object itself.

A variant can hold multiple alternatives of the same type, ...