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Exploring Category Theory with Haskell: Challenge Problem

Posted on 2009-10-22 by Travis Cardwell :: comments enabled

Here’s a little challenge to try before the presentation on October 29th. For those of you who have studied category theory, it will be very simple, but it should be more fun for the rest of you. All you need to solve the challenge is your mind, though a pencil and paper may help.

During my presentation I will give a whiteboard overview of introductory category theory as applied to finite sets. I will then present the Haskell code that I wrote, along with the solution to the challenge problem.1

The Problem

How many idempotent endomaps exist for any finite set of a given size?

In not-so-mathematical terms, find the number of functions from a given finite set to itself where f(x) == f(f(x)). Your answer should be an equation with the size of the finite set as the parameter.


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CUFP Videos and Summary Available

Posted on 2009-09-24 15:35 JST by Curt Sampson :: comments enabled

I mentioned last week that the CUFP 2009 slides are available. Don Stewart has now also posted his notes on CUFP as well, which go beyond the slides for detail for some of the talks.

If you have the time to watch them, the CUFP 2009 videos have also now been posted.


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ICFP 2009 Videos!

Posted on 2009-09-22 02:48 JST by Curt Sampson :: comments enabled

Darn, well, there you go. It turns out Malcom has been a very busy boy and not only put up the HIWS, but also has all of the ICFP 2009 up as well. Including mine. (I won’t dwell on how I look fat.)

I personally recommend Conal Eliot’s Beautiful Differentiation talk. It was truly beautiful, and had I had someone like this to teach me first year calculus, I probably would have a degree today.


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ICFP 2009 Haskell Implementors' Workshop Videos Available

Posted on 2009-09-22 00:08 JST by Curt Sampson :: comments enabled

Ah, yes, I was informed about this last week, but took my time posting about it, anyway, the presentation videos from the 2009 Haskell Implementors’ Workshop are now available.


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TSAC Meeting: 2009-09-24

Posted on 2009-09-21 22:55 JST by Curt Sampson :: comments enabled

As usual, TSAC will be meeting on the last Thursday of this month, September 24th, 2009, at 7:30 PM at the offices of Starling Software. Full information is available on the TSAC page.

This month, I’ll be giving a report on what went on at the 2009 International Conference on Functional Programming, which I attended around the beginning of this month. If there’s anything from the proceedings that looks especially interesting to you, drop me an e-mail and I’ll try to give it some extra attention.


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CUFP Slides Available

Posted on 2009-09-19 08:35 JST by Curt Sampson :: comments enabled

If you have a look at the program page for Commercial Users of Functional Programming 2009 you’ll find now that, as well as the abstracts, the slides for the talks have been made available. The videos for both these and other ICFP presentations are probably about a month away, according to Jim Grundy of the ACM.


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ICFP Slides and Papers Available

Posted on 2009-09-10 10:35 JST by Curt Sampson :: comments enabled

Since I’ve had a couple of requests, I’ve just posted the slides for both my ICFP 2009 presentation, Haskell in the Real World, and my Haskell Implementor’s Workshop presentation, My Dream GHC Environment.

Both presentations were videotaped, and the ICFP one, at least, is supposed to be available soon (perhaps on Google videos). The videos will no doubt be a lot more informative than my slides,


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Fame and Fortune

Posted on 2009-09-10 00:45 JST by Curt Sampson :: comments enabled

Wow. Someone I don’t even know discovered my paper and put up a blog post about it. That would be the Summary: Haskell in the Real World post from Ujihisa-san’s Standards blog.

How he found it I’m not sure, since ICFP Proceedings are not exactly as popular as Slashdot, and nor is my rather dry, academic writing style in this paper as anywhere near as exciting as Yaron Minsky’s Caml Trading presentation. So I’m especially enjoying the love.

I always knew Haskell would bring me fame and (soon, I hope) fortune.


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