3 ms·

The advantage of the Option type is that you don't need to check for nullability, you simply pattern match on Some(_) or None. A type of `some{T} | undefined` m

by angio 6y ago

The advantage of the Option type is that you don't need to check for nullability, you simply pattern match on Some(_) or None. A type of `some{T} | undefined` means that the expression can have values `Some(_)` or `None` or `undefined`, which defeats the point of the Option type!

masklinn 6y ago
Except Erlang doesn't have a none. Nor an undefined for that matter. So `some {T} | undefined` means exactly that, there is no underlying null pointer which could sneak up on you. `undefined` here is not built-in type or value of the language, it's a standard atom like any other. So are null, nil, value or false (although false does have a special status in that it's the customary output of boolean operations alongside true).
- angio 6y ago
  I'm aware of that, I was explaining why `some{T} | undefined` is problematic in Typescript. If you have a signature with both option type and undefined it's a signal of a code smell.
  - mbo 6y ago
    But `some{T}` isn't an option type, it's a member of the option type!
mbo 6y ago
> A type of `some{T} | undefined` means that the expression can have values `Some(_)` or `None` or `undefined` Can you please explain this further? Why is `None` an inhabitant of this union?