JSON parsing with Parsec

YaJSON.hs

module YaJSON where

import Text.Parsec
import qualified Text.Parsec.Token as Token
import qualified Text.Parsec.Language as Language
import qualified Data.Map as Map

language = Language.javaStyle
lexer = Token.makeTokenParser language

identifier = Token.identifier lexer
commaSep = Token.commaSep lexer
braces = Token.braces lexer
brackets = Token.brackets lexer
reservedOp = Token.reservedOp lexer
stringLiteral = Token.stringLiteral lexer
float = Token.float lexer
integer = Token.integer lexer

data JSON =
    JSONFloat Double |
    JSONInt Integer |
    JSONString String |
    JSONDict (Map.Map JSON JSON) |
    JSONList [JSON]
    deriving (Eq, Ord, Show)

json =
    fmap JSONFloat (try float) <|>
    fmap JSONInt (integer) <|>
    fmap JSONString (identifier <|> stringLiteral) <|>
    fmap (JSONDict . Map.fromList) (braces . commaSep $ pair) <|>
    fmap JSONList (brackets . commaSep $ json)
    where
    pair = do
        l <- json
        reservedOp ":"
        r <- json
        return (l, r)