Re: [Haskell-cafe] Knight Capital debacle and software correctness

On Sat, 4 Aug 2012, Clark Gaebel 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. oo--JS.

On Sat, Aug 4, 2012 at 2:04 PM, Jay Sulzberger wrote:

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On Sat, 4 Aug 2012, Clark Gaebel wrote:

Yes.

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Thank you!

Further, if you want:

Let us have two types s and t. Let _|_^s be the_|_ for type s, and let _|_^t be the _|_ for type t.

For which famous equivalences of the Haskell System are these two _|_ objects equivalent?

oo--JS.

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On Sat, Aug 4, 2012 at 1:47 PM, Jay Sulzberger wrote:

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On Sat, 4 Aug 2012, Jake McArthur wrote:

I feel like this thread is kind of surreal. Knight Capital's mistake

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was to use imperative programming styles? An entire industry is suffering because they haven't universally applied category theory to software engineering and live systems? Am I just a victim of a small troll/joke?

- Jake

ad application of category theory: No joke.

Atul Gawande's book The Checklist Manifesto deals with some of this:

http://us.macmillan.com/****thechecklistmanifesto/****AtulGawandehttp://us.macmillan.com/**thechecklistmanifesto/**AtulGawande <http://us.**macmillan.com/**thechecklistmanifesto/**AtulGawandehttp://us.macmillan.com/thechecklistmanifesto/AtulGawande

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In related news, for every type t of Haskell is it the case that something called "_|_" is an object of the type?

oo--JS.

On Sat, Aug 4, 2012 at 12:46 PM, Jay Sulzberger wrote:

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On Sat, 4 Aug 2012, Vasili I. Galchin wrote:

Hello Haskell Group,

> > I work in mainstream software industry. > > I am going to make an assumption .... except for Jane Street > Capital all/most "Wall Street" software is written in an imperative > language. > > Assuming this why is Wall Street not awaken to the dangers. As I > write, Knight Capital may not survive the weekend. > > > Regards, > > Vasili > >

I believe this particular mild error was in part due to a failure to grasp and apply category theory. There are several systems here:

1. The design of the code.

2. The coding of the code.

3. The testing of the code.

4. The live running of the code.

5. The watcher systems which watch the live running.

If the newspaper reports are to be believed, the watcher systems, all of them, failed. Or there was not even one watcher system observing/correcting/halting at the time of running.

Category theory suggests that all of these systems are worthy of study, and that these systems have inter-relations, which are just as worthy of study.

oo--JS.

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