mkscrg/Deep.hs

## README.md

      
    Raw
  

              README.md
            
          
    $ cabal sandbox init
$ cabal install aeson

$ ghci
Prelude> :set prompt "> "
> :set -XOverloadedStrings
> :l Deep.hs
[1 of 1] Compiling Deep             ( Deep.hs, interpreted )
Ok, modules loaded: Deep.

> -- some data:
> jsonTxt
"{\"foo\":{\"bar\":{\"baz\":\"deeeeeep\"}}}"

> -- go deep
> decodeP (top >>: "foo" >>: "bar" >>: "baz") jsonTxt :: Either String Text
Right "deeeeeep"

> -- continue parsing at depth
> let checkString = (\s -> when (s /= "quux") (fail $ "unexpected string: " ++ show s)) :: Text -> Parser ()
> decodeP (top >>: "foo" >>: "bar" >>: "baz" >=> checkString) jsonTxt
Left "unexpected string: \"deeeeeep\""


## Deep.hs
{-# LANGUAGE OverloadedStrings #-}
module Deep where

import Control.Monad
import Data.Aeson
import Data.Aeson.Types
import Data.ByteString.Lazy
import Data.Text


jsonTxt :: ByteString
jsonTxt = "{\"foo\":{\"bar\":{\"baz\":\"deeeeeep\"}}}"


decodeP :: (Value -> Parser a) -> ByteString -> Either String a
decodeP pf lbs = do
    jsonVal <- eitherDecode lbs
    parseEither (\v -> pf v) jsonVal

top :: FromJSON a => Value -> Parser a
top = parseJSON

(>>:) :: FromJSON a => (b -> Parser Object) -> Text -> (b -> Parser a)
pf >>: key = pf >=> (.: key)
infixl 6 >>:
	{-# LANGUAGE OverloadedStrings #-}
	module Deep where

	import Control.Monad
	import Data.Aeson
	import Data.Aeson.Types
	import Data.ByteString.Lazy
	import Data.Text


	jsonTxt :: ByteString
	jsonTxt = "{\"foo\":{\"bar\":{\"baz\":\"deeeeeep\"}}}"


	decodeP :: (Value -> Parser a) -> ByteString -> Either String a
	decodeP pf lbs = do
	jsonVal <- eitherDecode lbs
	parseEither (\v -> pf v) jsonVal

	top :: FromJSON a => Value -> Parser a
	top = parseJSON

	(>>:) :: FromJSON a => (b -> Parser Object) -> Text -> (b -> Parser a)
	pf >>: key = pf >=> (.: key)
	infixl 6 >>: