Enum @VERSION@ - Simulate Enums in Lua

This is a little module that simulates enumerated types in Lua.

Its API is very similar to the Python3 Enum API, although much more limited.

Example Usage

enum = require("enum")

sizes = {"SMALL", "MEDIUM", "BIG"}
Size = enum.new("Size", sizes)
print(Size) -- "<enum 'Size'>"
print(Size.SMALL) -- "<Size.SMALL: 1>"
print(Size.SMALL.name) -- "SMALL"
print(Size.SMALL.value) -- 1
assert(Size.SMALL ~= Size.BIG) -- true
assert(Size.SMALL < Size.BIG) -- error "Unsupported operation"
assert(Size[1] == Size.SMALL) -- true
Size[5] -- error "Invalid enum member: 5"

-- Enums cannot be modified
Size.MINI -- error "Invalid enum: MINI"
assert(Size.BIG.something == nil) -- true
Size.MEDIUM.other = 1 -- error "Cannot set fields in enum value"

-- Keys cannot be reused
Color = enum.new("Color", {"RED", "RED"}) -- error "Attempted to reuse key: 'RED'"

Installing

Using "classic" nix

If you are on NixOS, you can install this package from nix-stefano-m-overlays.

Using nix flakes

This package can be installed as a nix flake. It provides packages for the various versions of Lua shipped with nix as well as an overlay that adds the enum attribute to the Lua package sets.

---

NOTE

To ensure that the flake overlays are composable, enum is added directly to the top-level luaPackages. An unfortunate consequence is that enum will not be present in lua.pkgs. To use enum in lua.withPackages, one must refer to the top-level luaPackages.

For example, say that you want a Lua environment with enum and http, you need to do something like:

let
  # assume that enumOverlay is the overlay provided by the enum flake.
  pkgs = import <nixpkgs> {overlays = [enumOverlay];};
in
# http is present in lua.pkgs
# enum is not present in lua.pkgs
myLuaEnv = pkgs.lua.withPackages(ps: [ps.http pkgs.luaPackages.enum])

---

Using Luarocks

This package is published to Luarocks as enum and can be installed using

luarocks install enum