---SOLUTION
-- A JSON library written in Haskell, adapted from an example
-- from "Real World Haskell".

-- Note that the module name must match the name of the file.
module JSON (
  JValue(..), --The (..) means that we are exporting the type and all of its constructors
  toString,
  isNull,
  jsonRightTriangles)
where

data JValue = JString String
			| JNumber Double
			| JBool Bool
			| JNull
			| JObject [(String, JValue)]
			| JArray [JValue]
  deriving (Eq, Ord, Show)


--The type annotation indicates that the function takes a JValue and returns a String
toString :: JValue      -> String
toString (JString s)    = "\"" ++ s ++ "\""
toString (JNumber n)    = show n
toString (JBool True)   = "true"
toString (JBool False)  = "false"
toString JNull          = "null"
toString (JArray lst)   = "[" ++ list2str lst ++ "]"
toString (JObject obj)  = "{\n" ++ obj2str obj ++ "\n}"

list2str :: [JValue] -> String
list2str [] = ""
list2str (x:[]) = (toString x)
list2str (x:xs) = (toString x) ++ ",\n " ++ (list2str xs)

obj2str :: [(String, JValue)] -> String
obj2str [] = ""
obj2str ((k,v):[]) = k ++ ":" ++ toString v
obj2str ((k,v):xs) = k ++ ":" ++ toString v ++ "," ++ obj2str xs

isNull JNull  = True
isNull _      = False

jsonRightTriangles = JArray [ JObject [("a",JNumber a), ("b",JNumber b), ("c",JNumber c)] |
  a<-[1..10],
  b<-[1..10],
  c<-[1..10],
  a^2 + b^2 == c^2]