# [`On; `Off];;
- : [> `Off | `On ] list = [`On; `Off]

# `Number 1;;
- : [> `Number of int ] = `Number 1

# let f = function `On -> 1 | `Off -> 0 | `Number n -> n;;
val f : [< `Number of int | `Off | `On ] -> int = <fun>

# List.map f [`On; `Off];;
- : int list = [1; 0]