1 files changed, 13 insertions, 1 deletions

@@ -11,6 +11,16 @@ function eval.Env (inner, outer)
         local mt = {
                 __type = "Environment",
                 __index = outer,
+                __newindex =
+                        function (self, key, value)
+                                if rawget(self, key) then
+                                        -- Set the current environment's value
+                                        rawset(self, key, value)
+                                else
+                                        -- Set the outer value
+                                        getmetatable(self).__index[key] = value
+                                end
+                        end,
         }
         return setmetatable(inner, mt)
 end
@@ -54,8 +64,10 @@ function eval.eval (x, env)
                 if op == "quote" then
                         return args.car
                 elseif op == "define" or op == "def" then
-                        env[args.car] = eval.eval(args.cdr.car, env)
+                        rawset(env, args.car, eval.eval(args.cdr.car, env))
                         return nil
+                elseif op == "set!" then
+                        env[args.car] = eval.eval(args.cdr.car, env)
                 elseif op == "lambda" or op == "lam" then
                         return eval.Proc(args.car, args.cdr, env)
                 elseif op == "if" then