Proposal: die to System.Exit (and/or Prelude)

Vo Minh Thu noteed at
Sat Dec 14 11:09:20 UTC 2013

2013/12/14 Simon Hengel <sol at>:
> Hi!
> I propose to add
>     die :: String -> IO ()
>     die err = hPutStrLn stderr err >> exitFailure
> to System.Exit.
> Reasoning:
> (1) It's a frequently required functionality.  Almost every command-line
>     program has code similar to this.
> (2) The definition is relatively short, but in addition to the
>     definition, you need two import statements.
> (3) It's frequently done wrong (e.g. writing to stdout instead of
>     stderr, or not using exitFailure, or both).
> I haven't done any extensive research on Hackage, but I quickly looked
> at Haddock.  Here we have a definition of die [1], but we also print to
> stdout at a couple of place and then call exitFailure [2].
> Personally, I think it should be re-exported from Prelude.  But this may
> be controversial.  So let's have two separate votes:

Isn't your `die` function a special case of `error :: String -> a`,
which is in the Prelude ?

I think variants of what you propose are often used: different exit
codes, not exiting and flushing stderr, displaying an arbitrary `Show
a` instead of `String`, using `Text`, and so on.

Actually I think some (all ?) `IO` things from the Prelude should not
be in the Prelude. For instance I may want to use the `bytestring`

- 1 (for both)


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