Built in int -> enum

[mpope9]

This could exist in the language and I am missing it, but it seems there isn't a way to directly map a number to a type. One example that I find this useful in is Days of the week, where 1-7 could represent a day. What is currently needed is case statements to achieve mappings between custom types (correct me if I am wrong).

pub type Weekday {
  Monday
  Tuesday
}

pub create_date(d: Int) {
  case d {
    1 -> Ok(Monday)
    2 -> Ok(Tuesday)
    _ -> Error("Invalid date")
  }
}

Which is fine for 7 days of the week. But imagine when RPC mappings are desired, or a large enum is defined.

A solution could look something similar to this:

Weekday@2 == Tuesday
Weekday@3 == Error("Invalid Custom Type Postion")

Where some similar erlang code could be generated:

%% [email protected]
-define(WEEKDAY, [monday, tuesday]).

-define(AT_WEEKDAY(index), lists:nth(index, ?WEEKDAY)).

%% [email protected]
...
try ?AT_WEEKDAY(2) of
   Day -> Day
catch
   {error, "Invalid Custom Type Position")
end.

Unless this exists already?

[lpil]

It does not already exist but it does align well with some ideas I have for derived functions. We can add something like this is the future. :)

[mpope9]

Right on :D