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# README
## CSV Files and Haskell
CSV files are the de-facto standard in many cases of data transfer,
particularly when dealing with enterprise application or disparate database
systems.
While there are a number of csv libraries in Haskell, at the time of this
project's start in 2010, there wasn't one that provided all of the following:
* Full flexibility in quote characters, separators, input/output
* Constant space operation
* Robust parsing and error resiliency
* Fast operation
* Convenient interface that supports a variety of use cases
This library is an attempt to close these gaps.
## This package
csv-conduit is a conduits based CSV parsing library that is easy to
use, flexible and fast. Furthermore, it provides ways to use
constant-space during operation, which is absolutely critical in many
real world use cases.
### Introduction
* The CSVeable typeclass implements the key operations.
* CSVeable is parameterized on both a stream type and a target CSV row type.
* There are 2 basic row types and they implement *exactly* the same operations,
so you can chose the right one for the job at hand:
- type MapRow t = Map t t
- type Row t = [t]
* You basically use the Conduits defined in this library to do the
parsing from a CSV stream and rendering back into a CSV stream.
* Use the full flexibility and modularity of conduits for sources and sinks.
### Speed
While fast operation is of concern, I have so far cared more about correct
operation and a flexible API. Please let me know if you notice any performance
regressions or optimization opportunities.
### Usage Examples
#### Example #1: Basics Using Convenience API
{-# LANGUAGE OverloadedStrings #-}
import Data.Conduit
import Data.Conduit.Binary
import Data.Conduit.List as CL
import Data.CSV.Conduit
-- Just reverse te columns
myProcessor :: Conduit (Row Text) m (Row Text)
myProcessor = CL.map reverse
test :: IO ()
test = runResourceT $
transformCSV defCSVSettings
(sourceFile "input.csv")
myProcessor
(sinkFile "output.csv")
#### Example #2: Basics Using Conduit API
{-# LANGUAGE OverloadedStrings #-}
import Data.Conduit
import Data.Conduit.Binary
import Data.CSV.Conduit
myProcessor :: Conduit (Row Text) m (Row Text)
myProcessor = undefined
-- Let's simply stream from a file, parse the CSV, reserialize it
-- and push back into another file.
test :: IO ()
test = runResourceT $
sourceFile "test/BigFile.csv" $=
intoCSV defCSVSettings $=
myProcessor $=
fromCSV defCSVSettings $$
sinkFile "test/BigFileOut.csv"
|
