It's possible to write something like `std::unique_function` (which uniquely owns the stored callable and can be moved but not copied). That's often preferable

It's possible to write something like `std::unique_function` (which uniquely owns the stored callable and can be moved but not copied). That's often preferable for storing functors. Example: https://github.com/facebook/folly/blob/main/folly/docs/Function.md https://github.com/facebook/folly/blob/main/folly/docs/Funct...