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diff --git a/Tools/LuaMacro/macro/lib/class.lua b/Tools/LuaMacro/macro/lib/class.lua
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+----
+-- a basic class mechanism.
+-- Used for some of the demonstrations; the `class` macro in the `module`
+-- package uses it.  It provides a single function which returns a new 'class'.
+-- The resulting object can be called to generate an instance of the class.
+-- You may provide a base class for single inheritance; in this case, the functions
+-- of the base class will be copied into the new class' metatable (so-called 'fat metatable')
+--
+-- Example:
+--
+--     local class = require 'macro.lib.class'
+--     A = class()
+--     function A._init(name) self.name = name end
+--     a = A("hello")
+--     assert(a.name == "hello")
+--
+-- @module macro.lib.class
+
+return function (base)
+  -- OOP with single inheritance
+  local klass,cmt = {},{}
+  if base then -- 'fat metatable' inheritance
+    for k,v in pairs(base) do klass[k] = v end
+  end
+  klass.__index = klass
+  -- provide a callable constructor that invokes user-supplied ctor
+  function cmt:__call(...)
+    local obj = setmetatable({},klass)
+    if klass._init then klass._init(obj,...)
+    elseif base and base._init then base._init(base,...) end
+    return obj
+  end
+  setmetatable(klass,cmt)
+  return klass
+end