Improved indentation by using tab. Added module variable SPARSELIMIT to control the length threshold of sparse arrays. Some bug fixes and improvements as suggested by @appgurueu

json.lua

@@ -22,7 +22,10 @@
 -- SOFTWARE.
 --
 
-local json = { _version = "0.1.2" }
+local json = { 
+	_version = "0.1.2" ,
+	SPARSELIMIT = 100,			-- To set the limit on how long sparse arrays can be
+}
 
 -------------------------------------------------------------------------------
 -- Encode
@@ -70,7 +73,7 @@ local function encode_table(val, stack)
 	local nLen = 0
 	local count = 0
 	for k,v in pairs(val) do
-		if (type(k) ~= "number" or k<=0) and not (k == "n" and type(v) == "number") then
+		if (type(k) ~= "number" or k<=0 or k%1 ~= 0) and not (k == "n" and type(v) == "number") then
 			array = nil
 			break	-- Treat as object
 		else
@@ -87,7 +90,7 @@ local function encode_table(val, stack)
 	if nLen > length then
 		length = nLen
 	end
-	if array and not (length > 100 and count ~= length) then	-- Check Array detected but sparse > 100 length then treat as object
+	if array and not (length > SPARSELIMIT and count ~= length) then	-- Check Array detected but sparse > 100 length then treat as object
 		-- Encode
 		for i=1,length do
 			table.insert(res, encode(val[i], stack))
@@ -97,11 +100,6 @@ 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
@@ -120,7 +118,7 @@ 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 tostring(val)
+	return string.format("%.14g",val)
 end