Better Lua vectors

Author: rtoal

lua/vectors.lua

@@ -1,33 +1,33 @@
-Vector = (function (class, meta, prototype)
+Vector = (function (class)
+  local meta = {
+    __add = function(self, v)
+      return class.new(self.i + v.i, self.j + v.j)
+    end,
+    __mul = function(self, v)
+      return self.i * v.i + self.j * v.j
+    end,
+    __tostring = function(self)
+      return string.format("<%g,%g>", self.i, self.j)
+    end,
+    __index = {
+      magnitude = function(self)
+        return math.sqrt(self.i * self.i + self.j * self.j)
+      end
+    },
+  }
+
   class.new = function (i, j)
     return setmetatable({i = i, j = j}, meta)
   end
 
-  prototype.magnitude = function (self)
-    return math.sqrt(self.i * self.i + self.j * self.j)
-  end
-
-  meta.__index = prototype
-
-  meta.__add = function (self, v)
-    return class.new(self.i + v.i, self.j + v.j)
-  end
-
-  meta.__mul = function (self, v)
-    return self.i * v.i + self.j * v.j
-  end
-
-  meta.__tostring = function (self)
-    return string.format('<%g,%g>', self.i, self.j)
-  end
-
   return class
-end)({}, {}, {})
+end)({})
 
 u = Vector.new(3, 4)
 v = Vector.new(-5, 10)
 assert(tostring(u) == "<3,4>")
 assert(tostring(v) == "<-5,10>")
+assert(u.i == 3)
 assert(u.j == 4)
 assert(u:magnitude() == 5.0)
 assert(tostring(u + v) == "<-2,14>")