diff --git a/json.lua b/json.lua
index 711ef78..3ff9893 100644
--- a/json.lua
+++ b/json.lua
@@ -64,22 +64,24 @@ local function encode_table(val, stack)
   if stack[val] then error("circular reference") end
 
   stack[val] = true
+  -- Check whether to treat as a array or object
+  local array = true
+  local length = 0
+  for k in pairs(val) do
+	if type(k) ~= "number" or k<=0 then
+		array = nil
+		break	-- Treat as object
+	else
+		if k > length then 
+			length = k
+		end
+	end
+  end
 
-  if rawget(val, 1) ~= nil or next(val) == nil then
-    -- Treat as array -- check keys are valid and it is not sparse
-    local n = 0
-    for k in pairs(val) do
-      if type(k) ~= "number" then
-        error("invalid table: mixed or invalid key types")
-      end
-      n = n + 1
-    end
-    if n ~= #val then
-      error("invalid table: sparse array")
-    end
+  if array then
     -- Encode
-    for i, v in ipairs(val) do
-      table.insert(res, encode(v, stack))
+    for i=1,length do
+      table.insert(res, encode(val[i], stack))
     end
     stack[val] = nil
     return "[" .. table.concat(res, ",") .. "]"
@@ -87,9 +89,11 @@ local function encode_table(val, stack)
   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")
       end
+	  ]]
       table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
     end
     stack[val] = nil
@@ -108,7 +112,7 @@ local function encode_number(val)
   if val ~= val or val <= -math.huge or val >= math.huge then
     error("unexpected number value '" .. tostring(val) .. "'")
   end
-  return string.format("%.14g", val)
+  return tostring(val)
 end