Sort CSV

sort_csv.hs

{-# LANGUAGE ScopedTypeVariables #-}

module Main where

import           Control.Monad.ST
import qualified Data.ByteString.Lazy         as BL
import           Data.Csv
import           Data.List                    (intercalate)
import qualified Data.Vector                  as V
import qualified Data.Vector.Algorithms.Intro as VA
import           System.Environment           (getArgs)

main :: IO ()
main = do
    (fileName:_) <- getArgs
    csvData <- BL.readFile fileName
    case decode False csvData of
        Left err -> putStrLn err
        Right v -> go v
  where
    go :: V.Vector (String,String,String,String) -> IO ()
    go v = V.forM_ (sort v) $ \ (a,b,c,d) -> putStrLn $ intercalate "," [a,b,c,d]
    sort v = runST $ do
      mv <- V.thaw v
      VA.sortBy compare mv
      V.freeze mv