[Haskell-cafe] Haskell with all the safeties off

David Feuer david.feuer at gmail.com
Fri Sep 7 18:06:00 CEST 2012

On Sep 7, 2012 2:00 AM, "Edward Z. Yang" <ezyang
<ezyang at mit.edu>@<ezyang at mit.edu>
mit.edu <ezyang at mit.edu>> wrote:
> Haskell already does this, to some extent, in the design of imprecise
> exceptions.  But note that bottom *does* have well defined behavior, so
> these "optimizations" are not very desirable.

They're not *usually* desirable, but when the code has been proven not to
fall into bottom, there doesn't seem to be much point in ensuring that
things will work right if it does. This sort of thing only really makes
sense when using Haskell as a compiler target.

> Edward
> Excerpts from David Feuer's message of Thu Sep 06 19:35:43 -0400 2012:
> > I have no plans to do such a thing anytime soon, but is there a way to
> > GHC to allow nasal demons to fly if the program forces bottom? This
mode of
> > operation would seem to be a useful optimization when compiling a
> > produced by Coq or similar, enabling various transformations that can
> > bottom into non-bottom, eliminating runtime checks in incomplete
> > etc.
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