MoonScript example #1

class.lua

local Object
do
  local _base_0 = {
    __inherited = function(self, child)
      for k, v in pairs(self.__base) do
        child.__base[k] = child.__base[k] or v
      end
    end
  }
  _base_0.__index = _base_0
  local _class_0 = setmetatable({
    __init = function() end,
    __base = _base_0,
    __name = "Object"
  }, {
    __index = _base_0,
    __call = function(cls, ...)
      local _self_0 = setmetatable({}, _base_0)
      cls.__init(_self_0, ...)
      return _self_0
    end
  })
  _base_0.__class = _class_0
  Object = _class_0
end
local Animal
do
  local _parent_0 = Object
  local _base_0 = {
    meep = function(self)
      return print(tostring(self.name) .. " is currently " .. tostring(self.status) .. ".")
    end,
    __tostring = function(self)
      return tostring(self.__class.__name) .. ": " .. tostring(self.name)
    end
  }
  _base_0.__index = _base_0
  setmetatable(_base_0, _parent_0.__base)
  local _class_0 = setmetatable({
    __init = function(self, name, status)
      if name == nil then
        name = 'Unknown animal'
      end
      if status == nil then
        status = 'not on meep'
      end
      self.name, self.status = name, status
    end,
    __base = _base_0,
    __name = "Animal",
    __parent = _parent_0
  }, {
    __index = function(cls, name)
      local val = rawget(_base_0, name)
      if val == nil then
        return _parent_0[name]
      else
        return val
      end
    end,
    __call = function(cls, ...)
      local _self_0 = setmetatable({}, _base_0)
      cls.__init(_self_0, ...)
      return _self_0
    end
  })
  _base_0.__class = _class_0
  if _parent_0.__inherited then
    _parent_0.__inherited(_parent_0, _class_0)
  end
  Animal = _class_0
end
local SpeakingAnimal
do
  local _parent_0 = Animal
  local _base_0 = {
    speak = function(self)
      return print(tostring(self.name) .. " says " .. tostring(self.sound) .. ".")
    end
  }
  _base_0.__index = _base_0
  setmetatable(_base_0, _parent_0.__base)
  local _class_0 = setmetatable({
    __init = function(self, super)
      if _parent_0 == nil then
        super = 'giraffe noises'
      end
      self.super = super
      return _parent_0.__init(self, self.name, self.status)
    end,
    __base = _base_0,
    __name = "SpeakingAnimal",
    __parent = _parent_0
  }, {
    __index = function(cls, name)
      local val = rawget(_base_0, name)
      if val == nil then
        return _parent_0[name]
      else
        return val
      end
    end,
    __call = function(cls, ...)
      local _self_0 = setmetatable({}, _base_0)
      cls.__init(_self_0, ...)
      return _self_0
    end
  })
  _base_0.__class = _class_0
  if _parent_0.__inherited then
    _parent_0.__inherited(_parent_0, _class_0)
  end
  SpeakingAnimal = _class_0
end
local Dog
do
  local _parent_0 = SpeakingAnimal
  local _base_0 = { }
  _base_0.__index = _base_0
  setmetatable(_base_0, _parent_0.__base)
  local _class_0 = setmetatable({
    __init = function(self, name, status)
      if status == nil then
        status = 'barking'
      end
      self.name, self.status = name, status
      self.sound = ('roof '):rep(4) .. 'roof'
      return _parent_0.__init(self, self.sound)
    end,
    __base = _base_0,
    __name = "Dog",
    __parent = _parent_0
  }, {
    __index = function(cls, name)
      local val = rawget(_base_0, name)
      if val == nil then
        return _parent_0[name]
      else
        return val
      end
    end,
    __call = function(cls, ...)
      local _self_0 = setmetatable({}, _base_0)
      cls.__init(_self_0, ...)
      return _self_0
    end
  })
  _base_0.__class = _class_0
  local self = _class_0
  self.alignment = 'good'
  if _parent_0.__inherited then
    _parent_0.__inherited(_parent_0, _class_0)
  end
  Dog = _class_0
end
local Cat
do
  local _parent_0 = SpeakingAnimal
  local _base_0 = { }
  _base_0.__index = _base_0
  setmetatable(_base_0, _parent_0.__base)
  local _class_0 = setmetatable({
    __init = function(self, name, status)
      if status == nil then
        status = 'sleeping'
      end
      self.name, self.status = name, status
      self.sound = 'meow'
      return _parent_0.__init(self, self.sound)
    end,
    __base = _base_0,
    __name = "Cat",
    __parent = _parent_0
  }, {
    __index = function(cls, name)
      local val = rawget(_base_0, name)
      if val == nil then
        return _parent_0[name]
      else
        return val
      end
    end,
    __call = function(cls, ...)
      local _self_0 = setmetatable({}, _base_0)
      cls.__init(_self_0, ...)
      return _self_0
    end
  })
  _base_0.__class = _class_0
  local self = _class_0
  self.alignment = 'evil'
  if _parent_0.__inherited then
    _parent_0.__inherited(_parent_0, _class_0)
  end
  Cat = _class_0
end
local suushi
do
  local _with_0 = Cat('Suushi')
  _with_0.age = 7
  _with_0:meep()
  _with_0:speak()
  _with_0.status = 'scared'
  _with_0:meep()
  suushi = _with_0
end
local ozzy
do
  local _with_0 = Dog('Ozzy')
  _with_0.age = 10
  _with_0:meep()
  _with_0:speak()
  ozzy = _with_0
end
local unknown = Animal()
unknown:meep()
print(suushi)
print(ozzy)
return print(unknown)

class.moon

-- Meep! It's twitter for animals.

class Object
  -- __inherited method is necessary if you want children to inherit metamethods
  __inherited: (child) =>
    for k,v in pairs @__base
      -- the or= operator only assigns if the left-hand-side is false/nil
      child.__base[k] or= v

class Animal extends Object
  -- functions/methods can take default arguments
  -- new is called with the creation of a new object
  -- @ is an alias for 'self'
  -- if followed by a variable name it is an alias for 'self.'
  new: (@name='Unknown animal', @status='not on meep') =>
    -- this is empty but that's OK!

  -- methods are defined by the fat arrow =>
  meep: =>
    print "#{ @name } is currently #{ @status }."

  -- __tostring metamethod is necessary to pretty print the object
  -- @@ is an alias for self.__class (ie the object's class)
  __tostring: => "#{ @@__name }: #{ @name }"

class SpeakingAnimal extends Animal
  new: (@super='giraffe noises') =>
    super @name, @status
  speak: =>
    print "#{ @name } says #{ @sound }."

class Dog extends SpeakingAnimal
  @alignment = 'good' --class variable
  new: (@name, @status='barking') =>
    @sound = 'roof '\rep(4) .. 'roof' -- object variable
    super @sound -- call our parent's new method

class Cat extends SpeakingAnimal
  @alignment = 'evil'
  new: (@name, @status='sleeping') =>
    @sound = 'meow'
    super @sound

-- the with block is a shortcut suushi.age = 7
suushi = with Cat 'Sushi'
  .age = 7
  \meep! -- and suushi\meep and so on
  \speak! -- \ is method invokation
  .status = 'scared'
  \meep!

oswald = with Dog 'Oswald'
  .age = 10
  \meep!
  \speak!

-- objects can also be created without the with block
unknown = Animal! -- ! is shorthand for ()
--Animal() calls __call() which in turn calls the class new method
unknown\meep!

print suushi -- print invokes an object's __tostring metamethod
print oswald
print unknown

start.lua

local create, yield, resume
do
  local _obj_0 = coroutine
  create, yield, resume = _obj_0.create, _obj_0.yield, _obj_0.resume
end

local permgen
permgen = function(a, n)
  if n == 0 then
    yield(a)
  end
  for i = 1, n do
    a[n], a[i] = a[i], a[n]
    permgen(a, n - 1)
    a[n], a[i] = a[i], a[n]
  end
end

local permute
permute = function(a)
  local coro = create(function()
    return permgen(a, #a)
  end)
  return function()
    local code, res = resume(coro)
    return res
  end
end

local evens
do
  local _accum_0 = { }
  local _len_0 = 1
  for i = 1, 8 do
    if i % 2 == 0 then
      _accum_0[_len_0] = i
      _len_0 = _len_0 + 1
    end
  end
  evens = _accum_0
end

local permutations
do
  local _accum_0 = { }
  local _len_0 = 1
  for t in permute(evens) do
    _accum_0[_len_0] = table.concat(t, ",")
    _len_0 = _len_0 + 1
  end
  permutations = _accum_0
end

print("We have " .. tostring(#permutations) .. " permutations:")

table.sort(permutations, function(a, b)
  return a < b
end)

return print(table.concat(permutations, "\n"))

start.moon

import create, yield, resume from coroutine

-- generate permutations
permgen = (a, n) ->
  if n == 0
    yield(a) --yield this permutation
  for i=1, n
    -- put i-th element as the last one
    a[n], a[i] = a[i], a[n]
    -- generate all permutations of the other elements
    permgen(a, n - 1)
    -- restore i-th element
    a[n], a[i] = a[i], a[n]

-- an iterator over all permutations of table
permute = (a) ->
  --coroutine.create takes a function
  coro = create -> permgen(a, #a)
  return -> --create an iterator
    code, res = resume(coro)
    return res

-- i = 1, 8 is range of the list comprehension
-- it yields i for each integer in the range when the condition is true.
evens = [i for i = 1, 8 when i % 2 == 0]

-- table.concat concatenates a table into a single string.
-- The second argument is the separator between each element.
-- in this case it will concatenate the table {2,4,6,8} into the string "2,4,6,8".
permutations = [table.concat t, "," for t in permute evens]

-- #{expression} is string iterpolation. It ONLY works within strings delimited by double quotes.
print "We have #{ #permutations } permutations:"

-- table.sort takes an optional second argument: a sorting function.
table.sort permutations, (a, b) -> a < b

-- and now we print them out in sorted order.
print table.concat permutations, "\n"