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-rw-r--r--eval.lua14
1 files changed, 13 insertions, 1 deletions
diff --git a/eval.lua b/eval.lua index f58c36e..9b1c315 100644 --- a/eval.lua +++ b/eval.lua
@@ -11,6 +11,16 @@ function eval.Env (inner, outer)
11 local mt = { 11 local mt = {
12 __type = "Environment", 12 __type = "Environment",
13 __index = outer, 13 __index = outer,
14 __newindex =
15 function (self, key, value)
16 if rawget(self, key) then
17 -- Set the current environment's value
18 rawset(self, key, value)
19 else
20 -- Set the outer value
21 getmetatable(self).__index[key] = value
22 end
23 end,
14 } 24 }
15 return setmetatable(inner, mt) 25 return setmetatable(inner, mt)
16end 26end
@@ -54,8 +64,10 @@ function eval.eval (x, env)
54 if op == "quote" then 64 if op == "quote" then
55 return args.car 65 return args.car
56 elseif op == "define" or op == "def" then 66 elseif op == "define" or op == "def" then
57 env[args.car] = eval.eval(args.cdr.car, env) 67 rawset(env, args.car, eval.eval(args.cdr.car, env))
58 return nil 68 return nil
69 elseif op == "set!" then
70 env[args.car] = eval.eval(args.cdr.car, env)
59 elseif op == "lambda" or op == "lam" then 71 elseif op == "lambda" or op == "lam" then
60 return eval.Proc(args.car, args.cdr, env) 72 return eval.Proc(args.car, args.cdr, env)
61 elseif op == "if" then 73 elseif op == "if" then