Re: [Haskell-cafe] MonadThrow and Either instance

6 Feb 2020


      On Thu, Feb 06, 2020 at 03:30:15PM +0000, PICCA Frederic-Emmanuel wrote:
...
So I need a function with this signature
pathAbsDir :: Text -> Either String (Path Abs Dir)
pathAbsDir t = do
  d <- try $ parseAbsDir (unpack . uncomment $ t)
  case d of
    Right v -> Right v
    Left e  -> Left (show e)
since I am using parseAbsDir wi this signature
parseAbsDir :: MonadThrow m => FilePath -> m (Path Abs Dir)
I would like to know how to write the patAbsDir method
Try (no pun intended):

    import Control.Monad.Catch.Pure (runCatch)
    import Data.Text (Text, unpack)
    import Path (Path, Abs, Dir, parseAbsDir)

    pathAbsDir :: Text -> Either String (Path Abs Dir)
    pathAbsDir t = do
        let d = runCatch $ parseAbsDir (unpack t)
        case d of
            Right v -> Right v
            Left e  -> Left $ show e

-- 
    Viktor.

Re: [Haskell-cafe] MonadThrow and Either instance

Viktor Dukhovni