Re: anything wrong by not using "module" ?

[Eduardo Ochs <eduardoochs@...>]

Hi Gaspard,

On Sat, Mar 26, 2011 at 12:10 PM, Gaspard Bucher <gaspard@teti.ch> wrote:
> Hi list !
> I am wondering if there is anything wrong when defining "classes" in this
> way (without using module):
> ======== file lk.Dir ===============================
> local lib = {sep = '/', ignore_pattern = '^[.]', type='lk.Dir'}
> lib.__index = lib
> lk.Dir = lib
> setmetatable(lib, {
>   -- new method
>  __call = function(table, arg)
>   local instance = {path = arg}
>   setmetatable(instance, lib)
>   return instance
> end})
> -- private
> local function some_helper(self, x, y)
>   -- ...
> end
> -- public
> function lib:glob(pattern)
>   -- ...
> end
> --- etc
> ======== file lk.Dir ===============================

I've been super-happy since about january using something
very similar to your idea:

  Class = {
      type   = "Class",
      __call = function (class, o) return setmetatable(o, class) end,
    }
  setmetatable(Class, Class)

  otype = function (o)  -- works like type, except on my "objects"
      local  mt = getmetatable(o)
      return mt and mt.type or type(o)
    end

Here's a demo:

  Vector = Class {
    type       = "Vector",
    __add      = function (V, W) return Vector {V[1]+W[1], V[2]+W[2]} end,
    __tostring = function (V) return "("..V[1]..","..V[2]..")" end,
    __index    = {
      norm = function (V) return math.sqrt(V[1]^2 + V[2]^2) end,
    },
  }
  v = Vector  {3,  4}  --  v = { 3,  4, __mt = Vector}
  w = Vector {20, 30}  --  w = {20, 30, __mt = Vector}
  print(v)             --> (3,4)
  print(v + w)         --> (23,34)
  print(v:norm())      --> 5
  print( type(v))      --> table
  print(otype(v))      --> Vector
  print( type(""))     --> string
  print(otype(""))     --> string

For more information see:

  http://angg.twu.net/blogme4/eoo.lua.html
  http://angg.twu.net/dednat5/eoo.lua.html

Cheers,
  Eduardo Ochs
  eduardoochs@gmail.com
  http://angg.twu.net/