[Haskell-cafe] csv one-liner

Graham Fawcett graham.fawcett at gmail.com
Tue Sep 30 14:54:59 EDT 2008

2008/9/30 wman <666wman at gmail.com>:
> I got asked how to do one particular thing in excel, which led to discssion
> with "our local MSOffice expert".
> During the discussion I stated that's it too much of a PITA and that I'd
> rather write a script.
> Long story short, I promised him a one-liner to "show the power and beauty
> of Haskell".
> I got the csv package from hackage, modified the parseCSVFromFile so it's
> returns IO CSV rather than IO (Either ParseError CSV), and finished with
> following code
> (writeFile "output.csv") =<< (liftM printCSV $ liftM (map updateLine) $
> parseCSVFromFile "input.csv")
> Is there room for improvement ?
> Could it still be made into one-liner without modifying the csv module (and
> without resorting to
> case parseCSVFromFile "input.csv" of { Left _ -> []; Right x -> x}
> kind of tricks) ?

How about:

parseCSVFromFile "in.csv" >>= return . either (const "error!")
printCSV >>= writeFile "out.csv"

using Data.Either (either) ?


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