Data commit

Task/Abstract-type/Lua/abstract-type-1.lua

@@ -0,0 +1,34 @@
+BaseClass = {}
+
+function class ( baseClass )
+    local new_class = {}
+    local class_mt = { __index = new_class }
+
+    function new_class:new()
+        local newinst = {}
+        setmetatable( newinst, class_mt )
+        return newinst
+    end
+
+    if not baseClass then baseClass = BaseClass end
+        setmetatable( new_class, { __index = baseClass } )
+
+    return new_class
+end
+
+function abstractClass ( self )
+    local new_class = {}
+    local class_mt = { __index = new_class }
+
+    function new_class:new()
+        error("Abstract classes cannot be instantiated")
+    end
+
+    if not baseClass then baseClass = BaseClass end
+        setmetatable( new_class, { __index = baseClass } )
+
+    return new_class
+end
+
+BaseClass.class = class
+BaseClass.abstractClass = abstractClass

Task/Abstract-type/Lua/abstract-type-2.lua

@@ -0,0 +1,8 @@
+A = class()         -- New class A inherits BaseClass by default
+AA = A:class()      -- New class AA inherits from existing class A
+B = abstractClass() -- New abstract class B
+BB = B:class()      -- BB is not abstract
+A:new()             -- Okay: New class instance
+AA:new()            -- Okay: New class instance
+B:new()             -- Error: B is abstract
+BB:new()            -- Okay: BB is not abstract