cassava's Introduction

cassava: A CSV parsing and encoding library

A CSV parsing and encoding library optimized for ease of use and high performance.

Usage example

Here's the two second crash course in using the library. Given a CSV file with this content:

John Doe,50000
Jane Doe,60000

here's how you'd process it record-by-record:

{-# LANGUAGE ScopedTypeVariables #-}

import qualified Data.ByteString.Lazy as BL
import Data.Csv
import qualified Data.Vector as V

main :: IO ()
main = do
    csvData <- BL.readFile "salaries.csv"
    case decode csvData of
        Left err -> putStrLn err
        Right v -> V.forM_ v $ \ (name, salary :: Int) ->
            putStrLn $ name ++ " earns " ++ show salary ++ " dollars"

If you want to parse a file that includes a header, like this one

name,salary
John Doe,50000
Jane Doe,60000

use decodeByName:

{-# LANGUAGE OverloadedStrings #-}

import Control.Applicative
import qualified Data.ByteString.Lazy as BL
import Data.Csv
import qualified Data.Vector as V

data Person = Person
    { name   :: String
    , salary :: Int
    }

instance FromNamedRecord Person where
    parseNamedRecord r = Person <$> r .: "name" <*> r .: "salary"

main :: IO ()
main = do
    csvData <- BL.readFile "salaries.csv"
    case decodeByName csvData of
        Left err -> putStrLn err
        Right (_, v) -> V.forM_ v $ \ p ->
            putStrLn $ name p ++ " earns " ++ show (salary p) ++ " dollars"

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