Option type

In some programming languages, an option type is a polymorphic type (i.e., a type that holds a generic type) that represents an optional value. Either the containing variable will hold a “nothing” type, or it will hold “some” value.

For example, for an option i32 type, we could have either None or Some(10).

The point of this is clear. If we work with data where it may not have a value, we can set it as None instead of storing a ground truth illegal value (like nullptr).

Option types are supported mainly in functional programming languages like Rust, Haskell, Scala, and OCaml. In addition, it’s now supported in starting in C++17.

• In Rust: Some(<T>), None, as the Option<T> enum.
• In C++: std::optional<T>.