λondon HUG

Next meeting: Paradise, a DSEL for derivatives pricing

The next meeting of the London Haskell User Group will be on Wednesday 25th June from 6:30PM at City University. Lennart Augustsson from Credit Suisse will be talking about his work there:

Creating a new pricing model for a financial derivative model consists of plumbing together generic low level analytics and creating a user friendly interface for the model.

The low level analytics is typically written in C++ and the user interface is often Excel.

We have developed a domain specific embedded language in Haskell for creating pricing models.

The programmer of the pricing model make a high level description of how to put the analytics together and what the user interface should look like, and from this the pricing model is generated.

I’m not sure if Neil will be available to video it this time, so if anyone else has the required equpiment and would like to volunteer to do so, that’d be great!

Edit: I’d accidentally disabled comments on this post. Now fixed, just in case anyone was desperate to make one!

Darcs patch theory and GADTs with Ganesh Sittampalam

Welcome HUGgers, and Happy 2008!

The next meeting of the Haskell User Group will be on Wednesday 23rd January from 6:30PM at City University. Many thanks to Ganesh Sittampalam of Credit Suisse, who will be speaking to us about “Darcs patch theory and GADTS”. Here is the abstract:

Darcs is a distributed version control system written in Haskell, noted for its unique “patch theory”, which provides a principled foundation for manipulating changes. In this talk I’ll introduce darcs briefly, talk about patch theory, and explain how recent development work for the upcoming darcs 2 release has made use of Haskell’s Generalised Algebraic Datatypes to eliminate certain classes of programming errors. No prior knowledge of GADTs will be assumed.

UPDATE: We will be in room AG04, as before. On entering the building turn right, and AG04 is a few doors along on the right hand side.

Jeremy Gibbons: Design Patterns as Higher-Order Datatype-Generic Programs

It’s meeting time again! The next meeting of the HUG will be on 14th November from 6:30PM at City University. Dr Jeremy Gibbons from the Oxford University Computing Laboratory will be giving a talk entitled Design Patterns as Higher-Order Datatype-Generic Programs. Here is the abstract:

Design patterns are reusable abstractions in object-oriented software. However, using current programming languages, these elements can only be expressed extra-linguistically: as prose, pictures, and prototypes. We believe that this is not inherent in the patterns themselves, but evidence of a lack of expressivity in the languages of today. We expect that, in the languages of the future, the code part of design patterns will be expressible as reusable library components. Indeed, we claim that the languages of tomorrow will suffice; the future is not far away. The necessary features are higher-order and datatype-generic constructs; these features are already or nearly available now. We argue the case by presenting higher-order datatype-generic programs capturing Origami, a small suite of patterns for recursive data structures.

See the venue page for details of how to get there. No specific room number has been allocated yet, so look out for signs or other recognisable Haskellers when you get there.

October pubmeet

Following the usual schedule of alternating between talks and pure pubmeets,
the next meeting will be in the Slaughtered Lamb from 6:30pm on Tuesday 30th
October. Hope to see you there!

Meeting reminder and abstract

Just a quick reminder that the next London HUG meeting is coming up on Thursday 20th September at City University from 6:30PM. Matthew and Tristan have sent me an abstract for their talk, as follows:

Take 2 PhD students who have never programmed in the IO Monad before, lock them in an office for 3 months, and let them loose with Haskell. In this talk we show our attempt at writing a classic tron game with a twist - and show some pitfalls we fell into and lessons learned. We then took some time to reflect, and decided to start to remake a nuclear war game, again with a twist - and will show our progress, plans and invite discussion on design idioms.

OpenGL demos included.”

Also, Dr Ross Paterson will be giving a talk on finger trees.

See you there!

Next Meeting 20th September

I’m pleased to announce that the next London HUG meeting will be on Thursday 20th September at City University, starting 6:30PM. This time we have two great talks for you.

Firstly, Dr Ross Paterson of City Uni will talk about finger trees. To quote from his abstract:

“We introduce 2-3 finger trees, a functional representation of persistent sequences supporting access to the ends in amortized constant time, and concatenation and splitting in time logarithmic in the size of the smaller piece. Representations achieving these bounds have appeared previously, but 2-3 finger trees are much simpler, as are the operations on them. Further, by defining the split operation in a general form, we obtain a general purpose data structure that can serve as a sequence, priority queue, search tree, priority search queue and more.”

Afterwards Matthew Sackman and Tristan Allwood, both PhD students at Imperial College, will talk about game design in Haskell. They will hopefully be giving live demonstrations of some of the games they have developed, depending on the availability of hardware. Abstract to follow.

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August 2007 Meeting

For those of you not subscribed to the mailing list: The next meeting is coming up. It will be a pub meet, and will happen next Wednesday (the 22nd). We’ll start at about 6:30, but people will most likely be turning up over most of the evening, so it doesn’t matter too much if you can’t make it there for then.

We haven’t entirely determined a location yet, but it’s looking increasingly likely that we’ll default to the slaughtered lamb again.

Update: Owing to a total lack of alternative suggestions, looks like we’re in the slaughtered lamb again! I’ll bring a sign saying “London HUG” so people can recognise us, but prior experience suggests it’s not hard to spot a large crowd of functional programmers.

News: Meeting no. 3 and Mailing List

Hello HUGgers! It’s time for another meeting, and this time we’re back at City University on Wednesday 25th July from 6:30PM. See the Venue page for more details of how to get there. This time we are in room A247.

This time, Lennart Augustsson has offered to give a short talk entitled “Djinn, generating code with magic?”. Sounds intriguing… however, we need more! I had offered to give a short talk on HXT, the Haskell XML Toolkit, but to my very great regret I will not be able to make it to the next meeting myself, as I will be in Japan. So we need more volunteers! Please send in your suggestions… remember, we are a small, friendly community, and a talk at any level would be very welcome.

In other news, Ganesh Sittampalam (Heffalump on IRC) has very helpfully set up two mailing lists. The first one is for announcements: this will be a low volume list, purely for announcing forthcoming meetings and so on. The second one is for discussions relating to the London HUG, for example which pub we should go to. Please try to keep general Haskell discussion off the London HUG list… they should happen in Haskell Cafe where other Haskellers outside London can benefit from them.

I will send a single personal email to everybody who previously registered for the HUG to invite you join the mailing lists. I apologize for the spam, but it’s the last one I will send.

HUG Meeting Number Two

Well, the vote results are in, and it seems you really want to meet up once a month rather than every two months. So be it! In the words of Winston Churchill, “democracy is the worst form of government except all the others that have been tried.”

Amazingly, it’s already been almost one month since the first HUG, which means we should have a meeting next week. However I don’t think it would be fair to ask anybody to prepare a talk at this short notice. I quite like the suggestion made by Ganesh that we could alternate between more informal meetings — which could be as simple as a gathering at the pub — and more structured meetings with talks and so on. This also helps those who have to travel from further afield, as they may prefer only to attend the structured talks and skip the pub (or vice versa).

Therefore, I would like to propose a trip to the pub on Wednesday 27 June from 6:30PM. Is everybody happy with the Slaughtered Lamb in Clerkenwell, or do you have any other suggestions?

For the next structured meeting let’s tentatively suggest Wednesday 25 July. Please everybody send in your suggestions for talks — either what you would like to talk about yourself, or what you would like to hear somebody else talk about — or any other ideas you might have. Thanks, and see you at the next HUG!

Thinking about Meeting Number Two

Well, the first meeting of the Haskell User Group was, I think, a great success. Simon’s talk was fascinating, as were the discussions in the pub afterwards.

However, I’d like to see if we can do better. Some of the feedback suggested that the talk went over some people’s heads, which is understandable since I think we had a number of Haskell newbies in the audience, and even a few who were merely Haskell-curious. I really would like the LHUG to be inclusive of those people, so I would hope that next time we can have a better mixture of introductory material along with some of the more advanced stuff.

Here’s my suggestion for next time. Rather than one marathon talk, lets have two short talks, perhaps just 20 to 30 minutes long. Ideally one of these would be more introductory while the other one is a little more advanced. After that I propose a debate on the subject:

“Why isn’t functional programming more widely used in industry?”

To get the ball rolling on the talks, I can offer to talk on the subject “XML Processing with HXT and Arrows”. Please have a think about whether there is anything you would like to talk about, and send in your suggestions. Hopefully you’ll come up with better ideas than mine, so I don’t have to stand up and speak.

You’ll notice on the sidebar of this site there is a poll about the frequency of HUG meetings. I know we did a show of hands during the first meeting, which indicated strong support for a monthly meeting, but I have since been persuaded that that might be overdoing it. The initial energy and excitement of a new user group can quickly dissipate, so let’s give everybody some time to contemplate the previous meeting before rushing into the next one each time. I think the talks and discussions will feel a lot fresher with a bi-monthly or quarterly meeting. Anyway, place your vote, or comment below, and we’ll go with whatever the majority decide.