Re: WARNING pragmas in `Prelude.undefined` and `Prelude.error`

I agree that `error`/`undefined` can be legitimate; however often this legitimacy rests on invariants that aren't necessary stable under change-types-and-fix-errors-until-things-type-check style refactoring! So after refactoring I'd like to switch on my `error`/`undefined` warnings temporarily.

On 23 Dec 2019, at 13:36, Andreas Abel wrote:

I am missing some context of this discussion, but if this is the question of whether using `undefined` and `error` can be legitimate, yes they can. If you know your invariants, you might want to write

fromMaybe undefined $ lookup key map

or

Map.findWithDefault undefined key map

knowing you put the key into the map and the lookup cannot fail.

On 2019-12-22 13:15, Zemyla wrote:

...

The most common legitimate usage for undefined I have is strictness: func x y | x `seq` False = undefined func x y = ... There's nothing else that would go there, and when it's compiled, the reference to undefined disappears. On Sun, Dec 22, 2019, 05:50 chessai . mailto:chessai1996@gmail.com> wrote: Right, it's been discussed before IIRC, and i know I've certainly given it passing thoughts. I think this isn't worth it because of breakage. Many people use -Wall -Werror, so I see this as a no-go. Thanka On Sun, Dec 22, 2019, 6:45 AM Vilem Liepelt mailto:vliepelt@futurefinance.com> wrote: Has there been any discussion about adding WARNING pragmas to `Prelude.undefined` and `Prelude.error`, as done in some custom preludes? I suppose this hasn't been done yet to avoid breaking existing code which makes "legitimate" use of those helpers? _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries _______________________________________________ Libraries mailing list Libraries@haskell.org mailto:Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

---

Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries