Haskell: How to use attoparsec in order to read a nested list from a ByteString

Question

I have a text file (~ 300 MB large) with a nested list, similar to this one:

[[4, 9, 11, 28, 30, 45, 55, 58, 61, 62, 63, 69, 74, 76, 77, 82, 87, 92, 93, 94,          


        

Answer 1

The data seems to be in JSON format, so you can use Data.Aeson decode function which works on ByteString

import qualified Data.ByteString.Lazy as BL
import Data.Aeson
import Data.Maybe

main = do fContents <- BL.readFile filePath 
          let numList = decode fContents :: Maybe [[Int]]
          putStrLn (show $ fromJust numList)