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October 8, 2018 16:08
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corner-cutting json parser
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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 |
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{ | |
"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" | |
} | |
} | |
} | |
} | |
} |
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