[Haskell-cafe] Knight Capital debacle and software correctness

[Jon Fairbairn]

Jay Sulzberger <jays at panix.com> writes:

> On Sat, 4 Aug 2012, Clark Gaebel <cgaebel at uwaterloo.ca> wrote:
>
>> As far as I know, you can't check "equivalence" of _|_. Since Haskell uses
>> _|_ to represent a nonterminating computation, this would be
>> synonymouswith solving the halting
>> problem.
>
> Ah, thanks.  I will attempt to think about this.

Also, one way of looking at type systems says that all these
_|_s are the same (but as Clark says, there’s no way within
Haskell to compare them). Haskell mangles this a little by
including non-value things other than non-termination in its
types.

   — Jón