enum.lua

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-- Simple enumerations for Lua.
-- 
-- @see file://libapptools/README.md
-- @author tdepke2
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---@alias Enum table<integer|string, string|integer>

---@docdef
-- 
-- Creates a new enumeration from a given table (matches keys to values and vice
-- versa). The given table is intended to use numeric keys and string values,
-- but doesn't have to be a sequence. An error is thrown if there are duplicate
-- values in the table.
-- Based on: https://unendli.ch/posts/2016-07-22-enumerations-in-lua.html
-- 
---@param t table<integer, string>
---@return Enum
---@nodiscard
local function enum(t)
  local result = {}
  for i, v in pairs(t) do
    if result[v] ~= nil then
      error("duplicate value \"" .. tostring(v) .. "\" defined in enum.", 2)
    end
    result[i] = v
    result[v] = i
  end
  return result
end

return enum