<p><br>
On Sep 7, 2012 2:00 AM, "Edward Z. Yang" <<a href="mailto:ezyang@mit.edu">ezyang</a><a href="mailto:ezyang@mit.edu">@</a><a href="mailto:ezyang@mit.edu">mit.edu</a>> wrote:<br>
><br>
> Haskell already does this, to some extent, in the design of imprecise<br>
> exceptions. But note that bottom *does* have well defined behavior, so<br>
> these "optimizations" are not very desirable.</p>
<p>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.</p>
<p>> Edward<br>
><br>
> Excerpts from David Feuer's message of Thu Sep 06 19:35:<a href="tel:43%20-0400%202012">43 -0400 2012</a>:<br>
> > I have no plans to do such a thing anytime soon, but is there a way to tell<br>
> > GHC to allow nasal demons to fly if the program forces bottom? This mode of<br>
> > operation would seem to be a useful optimization when compiling a program<br>
> > produced by Coq or similar, enabling various transformations that can turn<br>
> > bottom into non-bottom, eliminating runtime checks in incomplete patterns,<br>
> > etc.</p>