handle encoding of number based key properties

i was unable to encode a table due to some number based key properties.

i modified the encode function to check for number based keys in addition to the already present string based keys.

an error will still be returned if the key is neither string nor number based.

it works in my cases


Please see this link:
rxi#43 (comment)

Author: alexandro-rezakhani

json.lua

@@ -90,20 +90,22 @@ local function encode_table(val, stack)
       end
       -- Encode
       for i=1,length do
-        table.insert(res, encode(val[i], stack))
+        res[#res + 1] = encode(val[i], stack)
       end
       stack[val] = nil
       return "[" .. table.concat(res, ",") .. "]"
     else
       -- Treat as an object
       for k, v in pairs(val) do
-          --[[
-        if type(k) ~= "string" then
-          error("invalid table: mixed or invalid key types")
+        if type(k) == "string" then
+          res[#res + 1] = encode(k, stack) .. ":" .. encode(v, stack)
+        elseif type(k) == "number" then
+          res[#res + 1] = encode(string.format(k), stack) .. ":" .. encode(v, stack)
+        else
+          error("invalid table: mixed or invalid key types");
         end
-	    ]]
         if k ~= "_" then
-          table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
+          res[#res + 1] = encode(k, stack) .. ":" .. encode(v, stack)
         end
       end
       stack[val] = nil