Lua random class which is 'Lehmer RNG' formula based.

random.lua

-- See: https://en.wikipedia.org/wiki/Linear_congruential_generator
-- See: https://en.wikipedia.org/wiki/Lehmer_random_number_generator
-- Original Lehmer RNG construction
local m = 65537 -- (2 ^ 16) + 1,  a fermat prime
local a = 75 -- a primitive root modulo
local x0 = 65536 -- a seed number, greater than '0', less than 'm'
local md = m - 1 -- a floating-point devider

-- Lehmer random number generator formula
local function rng(x)
  return (x * a) % m
end

-- random min-max number formula
local function rmm(min, max, x)
  return min + (x % (max - min))
end

-- random min-max number formula
local function rmmf(min, max, x)
  return min + ((max - min) * x)
end

-- checks seed number is valid
local function iv(n)
  if type(n) ~= "number" then
    error("expected a number!")
  end
  if n <= 0 or n >= m then
    error("invalid seed number!")
  end
  if n % 1 ~= 0 then
    error("seed number should be an integer!")
  end
end

-- checks min, max number is valid
local function ivmmd(min, max)
  if type(min) ~= "number" or type(max) ~= "number" then
    error("expected a number!")
  end
  if min > max then
    error("invalid 'min'-'max' number!")
  end
end

-- checks min, max number is valid
local function ivmm(min, max)
  ivmmd(min, max)
  if min % 1 ~= 0 or max % 1 ~= 0 then
    error("seed number should be an integer!")
  end
end

local _r = {
  -- original seed, current seed
  ox = x0,
  cx = x0
}
-- get or set a seed value
-- Note: seed number can be between (0, 65537) a integer value
---@param n?   integer
---@return integer
function _r:seed(n)
  if n ~= nil then
    iv(n)
    self.ox, self.cx = n, n
  end
  return self.ox
end

-- get a random integer number between [min, max)
---@param min   integer
---@param max   integer
---@return integer
function _r:range(min, max)
  ivmm(min, max)
  self.cx = rng(self.cx)
  return rmm(min, max, self.cx)
end

-- get a random floating-point number between [min, max]
---@param min   number
---@param max   number
---@return number
function _r:rangef(min, max)
  ivmmd(min, max)
  self.cx = rng(self.cx)
  return rmmf(min, max, rmm(0, m, self.cx) / md)
end

-- returns a new instance with/without a seed number
-- Note: seed number can be between (0, 65537) a integer value
---@param seed?   integer
function _r:new(seed)
  local x = seed or x0
  iv(x)
  local _inst = setmetatable({ox = x, cx = x}, {__index = self})
  return _inst
end

-- returns an instance
return _r