Doji on Use Haskell for shell scripting

Comment on Use Haskell for shell scripting

The tutorial does a great job of explaining why this is interesting: http://hackage.haskell.org/package/turtle-1.0.0/docs/Turtle-...

For example, the pwd function returns a FilePath type rather than a String:

  Prelude Turtle> :type pwd
  pwd :: IO Turtle.FilePath

The datefile function is also typed:

  Prelude Turtle> :type datefile
  datefile :: Turtle.FilePath -> IO UTCTime

So this really does seem to structure the data passed between commands, instead of the "stringly typing" unix shells have historically been known for.

TazeTSchnitzel 11y

Are those types just aliases of String?

throwaway283719 11y

No. For example, a FilePath is (after resolving a few other type aliases)

  data Root
	  = RootPosix
	  | RootWindowsVolume Char
	  | RootWindowsCurrentVolume

  data FilePath = FilePath
	  { pathRoot        :: Maybe Root
	  , pathDirectories :: [String]
	  , pathBasename    :: Maybe String
	  , pathExtensions  :: [String]
	  }

marcosdumay 11y

What do you mean by "alias"?

Path carries String-like information, it can even be easily converted to and from strings. Yet, it's a strong type that won't let you write something like 'path </> file_contents' (although, with overloaded strings, you can do 'path </> "file_name"').

UTCTime is not String-like.

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