basic class simulacrum and basic hash object ... enjoy

gistfile1.lua

-- ----------------------------------------------------------------------------
-- "THE BEER-WARE LICENSE" (Revision 42):
-- <[email protected]> wrote this file. As long as you retain this notice you
-- can do whatever you want with this stuff. If we meet some day, and you think
-- this stuff is worth it, you can buy me a beer in return
-- ----------------------------------------------------------------------------

local table, string = require [[table]], require [[string]]

local type, pairs, rawset, setmetatable, getmetatable =
  type, pairs, rawset, setmetatable, getmetatable

local insert, remove, format = table.insert, table.remove, string.format

--
--
--
--
--

local classes = setmetatable({}, {__mode='k'})

local function deep_copy(t, dest)
  local t, r = t or {}, dest or {}
  for k,v in pairs(t) do
    if type(v) == 'table' and k ~= '__index' then
      r[k] = deep_copy(v)
    else
      r[k] = v
    end
  end
  return r
end

local function is(self, klass)
  local m = getmetatable(self)
  while m do 
    if m == klass then return true end
    m = m.super
  end
  return false
end

local function include(self, ...)
  if not ... then return end
  for k,v in pairs(...) do
    if self[k] then self[k] = nil end
    self[k] = v
  end
end

local function extends(self, ...)
  local meta = {}
  if ... then deep_copy(..., deep_copy(self, meta)) else deep_copy(self, meta) end
  setmetatable(meta, getmetatable(self))
  return meta
end

local function new_index(self, key, value)
  rawset(self, key, value)
  for i=1, #classes[self] do
    classes[self][i][key] = value
  end
end

local function class(base)
  local c, mt = {}, {}
  if type(base) == 'table' then
    for i,v in pairs(base) do c[i] = v end
    c.super = base
  end

  c.__index     = c
  c.is          = is
  c.extends     = extends
  c.include     = include
  mt.__newindex = new_index
  classes[c]    = {}

  mt.__call = function(self, ...)
    local obj = {}
    setmetatable(obj, c)
    if c.__init then c.__init(obj, ...) end
    return obj
  end

  if c.super then
    insert(classes[c.super], c)
  end

  setmetatable(c, mt)
  return c
end

--
--
--
--
--

local Hash = class()
Hash.__name = 'Hash'

function Hash:__init(bootstrap)
  rawset(self, '_i', 0)
  rawset(self, 'index', {})
  if 'table' == type(bootstrap) then
    for k,v in pairs(bootstrap) do
      self.index[k] = v
    end
  end  
end

function Hash:__newindex(key, val)
  if not self.index[key] then
    insert(self.index, key)
  end

  if nil == val then
    for i=1, #self.index do
      if self.index[i] == key then
        remove(self.index, i)
        self._i = self._i > 0 and (self._i - 1) or self._i
      end
    end
  end

  self.index[key] = val
end

function Hash:__index(key)
  return self.index[key]
end

function Hash:__pairs()
  self._i = 0
  local function iter(self)
    self._i = self._i + 1
    local k = self.index[self._i]
    if k then return k, self.index[k] end
  end
  return iter, self
end

function Hash:__len()
  return #self.index
end

function Hash:__sub(hash)
  if not('table' == type(hash) and
    rawget((getmetatable(hash) or {}), '__name') == 'Hash') then
    error(format("expecting hash, got a '%s'", type(hash)))
  end
  local new_index = {}
  for i=1, #self.index do
    if hash.index[self.index[i]] then
      insert(new_index, self.index[i])
      new_index[self.index[i]] = self.index[self.index[i]]
    end
  end
  return getmetatable(self)(new_index)
end

function Hash:__add(hash)
  if not('table' == type(hash) and
    rawget((getmetatable(hash) or {}), '__name') == 'Hash') then
    error(format("expecting hash, got a '%s'", type(hash)))
  end
  local new_hash = getmetatable(self)(self.index)
  for i=1, #hash.index do
    if not new_hash.index[hash.index[i]] then
      new_hash[hash.index[i]] = hash.index[hash.index[i]]
    end
  end
  return new_hash
end


local n, m = Hash(), Hash()

n['xico'] = 100
n['jose'] = 99
n['antonio'] = 'hey'
n['loco'] = 10.197
n.xico = 'Fuck!'

m.camila = 'Wow'
m.jose = 666

print(#n, n['xico'], n.antonio) print() -- 4 Fuck! hey

--[[
xico  Fuck!
jose  99
antonio hey
]]
for k,v in pairs(n) do
  if k == 'loco' then
    n[k] = nil -- delete "loco"
  else
    print(k, v)
  end
end print()

print(#n) print() -- 3

local g = n - m
local h = m - n
local z = n + m
local y = m + n

n.octopus = 'Genius'

-- jose  99
for k,v in pairs(g) do print(k, v) end print()
-- jose  666
for k,v in pairs(h) do print(k, v) end print()
--[[
xico  Fuck!
jose  99
antonio hey
camila  Wow
]]
for k,v in pairs(z) do print(k, v) end print()
--[[
camila  Wow
jose  666
xico  Fuck!
antonio hey
]]
for k,v in pairs(y) do print(k, v) end print()
--[[
xico  Fuck!
jose  99
antonio hey
octopus Genius
]]
for k,v in pairs(n) do print(k, v) end print()
-- camila Wow
-- jose 666
for k,v in pairs(m) do print(k, v) end print()