corner-cutting json parser

Main.hs

module Main where

import           Data.Functor                   ( ($>) )
import           Text.ParserCombinators.Parsec

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

main :: IO ()
main = do
    json <- readFile "test.json"
    let cjson = compress json
    -- NOTE: ignore rows and lines
    parseTest jsonParser cjson

compress :: String -> String
compress s = s >>= \c -> if elem c ignores then [] else [c]
    where ignores = [' ', '\n', '\t']

jsonParser :: Parser JValue
jsonParser =
    (const JNull <$> nullParser)
        <|> (JString <$> stringParser)
        <|> (JBool <$> boolParser)
        <|> (JNumber <$> numberParser)
        <|> (JArray <$> arrayParser)
        <|> (JObject <$> objectParser)

nullParser :: Parser String
nullParser = string "null"

stringParser :: Parser String
stringParser = between (char '"') (char '"') $ many c where c = noneOf ['"']

boolParser :: Parser Bool
boolParser = (string "true" $> True) <|> (string "false" $> False)

numberParser :: Parser Int
numberParser = read <$> many1 digit

arrayParser :: Parser [JValue]
arrayParser = between (char '[') (char ']') $ sepBy jsonParser (char ',')

objectParser :: Parser [(String, JValue)]
objectParser = between (char '{') (char '}') $ sepBy pair (char ',')
    where pair = (,) <$> stringParser <* char ':' <*> jsonParser

test.json

{
    "glossary": {
        "title": "example glossary",
		"GlossDiv": {
            "title": "S",
			"GlossList": {
                "GlossEntry": {
                    "ID": "SGML",
					"SortAs": "SGML",
					"GlossTerm": "Standard Generalized Markup Language",
					"Acronym": "SGML",
					"Abbrev": "ISO 8879:1986",
					"GlossDef": {
                        "para": "A meta-markup language, used to create markup languages such as DocBook.",
						"GlossSeeAlso": ["GML", "XML"]
                    },
					"GlossSee": "markup"
                }
            }
        }
    }
}