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Parsing Roman Numerals Redux

Posted on 2009-03-26 by Curt Sampson :: comments enabled

Well, I disagree with Bryan’s previous post post that the parsing was a “simple problem.” But I’ve finally implemented a Haskell solution, and have done quite the writeup about it (more than three times the length of the solution itself!).

Of course, after making sure that it was correct, I had to check its performance. While it’s not as good as I’d hoped (still more than five times slower than the C implementations we looked at), it’s respectable. Here’s the chart again, with my implementation’s peformance figures added:


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Parsing Roman Numerals

Posted on 2009-03-11 by Bryan Buecking :: comments enabled

Our February meeting had one presentation, by Travis, on parsing Roman Numerals. If you are not familiar with roman numerals, details can be found on Wikipedia 1. Luckily it was a simple problem, that kept everyone in the meeting involved.

The presenter, put together a couple versions of a parser, and later he compared the performance between them.


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Playing with Problems and the Y Combinator

Posted on 2009-02-03 by Curt Sampson :: comments enabled

The January 29th meeting was more successful and fun than I’d thought it might be. We had a good turnout (about a dozen), and though there was no official presentation, we spent quite a lot of time with ghci up on the big screen, playing about.

I thought I’d haul out the Haskell programming problem we ask employment candidates to submit when they send in a resume. I’d talked about it earlier, and John had sent me a few different versions already, since I’d offered him some beer in exchange. As it turned out, his friend Adrien had also sent some samples in, but to Bryan’s address instead of mine, so I didn’t see them. The various styles of solving the problem turned out to be rather interesting, from some clever and terse list processing to using a StateT monad transformer on the IO monad. (I still have mixed opinions about that one.)


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Digital Editions of Haskell Books

Posted on 2009-01-14 by Curt Sampson :: comments enabled

Those of us that are ACM members have access to a limited number of books from Safari and also a collection from Books24x7. The Safari collection doesn’t have much in the way of functional programming books, but Books24x7 has one of the better introductory Haskell books on-line: Graham Hutton’s Programming in Haskell. If you’ve got a membership, you can access it here.


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December Surprise Topic: Haskell FFI

Posted on 2009-01-12 by Curt Sampson :: comments enabled

The December 18th meeting, despite being near Christmas and a week earlier than the usual date, was surprisingly well-attended. We had close to a dozen people show up.

I had said that I would do a presentation on Haskell community resources, but ended up not having time to put that together (simple as you’d think it is) due to being plunged into a Haskell FFI project that I really needed to get finished. It turned out to be one of the more interesting things I’d done in Haskell, and it made interfacing with a Microsoft C API under Windows actually enjoyable, if you can believe that! (It’s an interface into the DDEML API, and we’ll be putting it up on Hackage at some point.)

So, since I’d been immersed in it for a solid week, anwyay, I thought perhaps it would be interesting for an impromptu presentation. It went over quite well, in large part I’m sure because the FFI is incredibly well designed.


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