New subject: Parse CSV / TSV file in Haskell - Unicode Characters

23 Oct 2014

      Hi,

I'm trying to parse a tab-delimited file using cassava/Data.Csv in Haskell.
However, I get problems if there are "strange" (Unicode) characters in my
CSV file. I'll get a parse error (endOfInput) then.

According to the command-line tool "file", my file has a "UTF-8 Unicode
text" decoding. My Haskell code looks like this:

{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE OverloadedStrings #-}

import qualified Data.ByteString as C
import qualified System.IO.UTF8 as U
import qualified Data.ByteString.UTF8 as UB
import qualified Data.ByteString.Lazy.Char8 as DL
import qualified Codec.Binary.UTF8.String as US
import qualified Data.Text.Lazy.Encoding as EL
import qualified Data.ByteString.Lazy as L

import Data.Text.Encoding as E

-- Handle CSV / TSV files with ...
import Data.Csv
import qualified Data.Vector as V

import Data.Char -- ord

csvFile :: FilePath
csvFile = "myFile.txt"

-- Set delimiter to \t (tabulator)
myOptions = defaultDecodeOptions {
              decDelimiter = fromIntegral (ord '\t')
            }

main :: IO ()
main = do
  csvData <- L.readFile csvFile
  case EL.decodeUtf8' csvData of
   Left err -> print err
   Right dat ->
     case decodeWith myOptions NoHeader $ EL.encodeUtf8 dat of
       Left err -> putStrLn err
       Right v -> V.forM_ v $ \ (category :: String ,
                               user :: String ,
                               date :: String,
                               time :: String,
                               message :: String) -> do
         print message

I tried using decodingUtf8', preprocessing (filtering) the input with
predicates from Data.Char, and much more. However the endOfFile error
persists.

My CSV-file looks like this:

a   -   -   -   RT USE " Kenny" • Hahahahahahahahaha. #Emmen #Brandstapel
a   -   -   -   Uhm .. wat dan ook ????!!!! 👋

Or more literally:

a\t-\t-\t-\tRT USE " Kenny" • Hahahahahahahahaha. #Emmen #Brandstapel
a\t-\t-\t-\tUhm .. wat dan ook ????!!!! 👋

The problem chars are the 👋 and • (and in my complete file, there are many
more of similar characters). What can I do, so that cassava / Data.Csv can
read my file properly?

I've also posted this question at StackOverflow a few days ago:
http://stackoverflow.com/questions/26499831/parse-csv-tsv-file-in-haskell-un...

Best,
Volker

Parse CSV / TSV file in Haskell - Unicode Characters

Volker Strobel

Johan Tibell

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