It should be somewhere here -> http://www.haskell.org/haskellwiki/Video_presentations -Amir On Tue, Jun 15, 2010 at 1:42 PM, Lyndon Maydwell wrote:

I don't think I can be of much help with regards to the questions, but would you be able to post a link to the SPJ lecture?

Thanks :-)

On Tue, Jun 15, 2010 at 4:08 PM, Amiruddin Nagri wrote:

...

My current project is about making an accounting engine that handles all the journal entries, transactions, portfolios etc. The communication with the engine is based on simple protocol, the things to be taken care of in the order are consistency, handling large data(performance)

...

availability.

I came across a video lecture by Simon Peyton Jones where he gives an example from Financial domain (derivatives etc) to explain how haskell is being used and the advantages provided.

I am interested in knowing if Haskell will be the right fit for my

...

My requirements are transactional nature, which I believe is one of the strengths of functional programming, also handling large data set and being available. there is no such requirement for partitioning of data and the application is going to be centrally hosted on a single server.

AFAIK OCaml and other functional languages are heavily used in financial domain, some of the reason are same as features I am looking for. I wanted some insight as to how Haskell is going to help me with my

and project. project.

...

Also there has been some concerns because of lazy evaluation in Haskell and memory leaks associated with it.

http://jlouisramblings.blogspot.com/2010/04/haskell-vs-erlang-for-bittorent-...

...

Also, if you have any suggestions of the choice of programming language, we have been looking into other functional languages like Scala and Clojure. But we have not dig deep on the performance aspects of these languages, if someone can shed a light on the pros- cons of these languages, it will help us very much to come to a decision.

-Regards, Amir

_______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners

I think Haskell would be an excellent choice. Several reasons come to mind: Given the arbitrary complexity of such projects, an EDSL describing book entries etc would be a very good fit for the project. As people have said once or twice, Haskell is a great fit for EDSLs If you want to get ambitious and scale this up to a multithreaded, multiuser environment, STM would be a very good concurrency model. This pretty much just leaves Haskell or Clojure. Finally, the type system of haskell is hugely useful to this project. Jane Street Capital (ocaml users and damned good at it) has a programming motto: make illegal transactions unrepresentative. The type systems of Haskell and OCaml let you structure this kind of project in a way to catch most of your bugs at compile time. So, I think Haskell is the perfect intersection of EDSL support, Concurrency, and powerful, static typing for the project. Good luck, keep us informed of your progress. Max On Jun 15, 2010, at 5:34 PM, Yitzchak Gale wrote:

Hi Amir,

Amiruddin Nagri wrote:

...

My current project is about making an accounting engine...

Take a look at the related but different project "hledger".

http://hackage.haskell.org/package/hledger http://hackage.haskell.org/package/hledger-lib

...

consistency, handling large data(performance) and availability... I am interested in knowing if Haskell will be the right fit for my project.

These things can certainly be achieved, and Haskell is a great platform for it. Reliability and assurance of correctness are very important for financial systems, and Haskell is especially good at providing them together with good performance.

However, keep in mind that you are undertaking a very ambitious project. There are a lot of little design decisions to be made along the way which, if made without a lot of previous experience in whatever language you are using, could lead to serious problems later on in a large system like this.

I recommend:

o Start with a less ambitious version of the project - a simpler prototype with less requirements, or components that can be developed as a stand-alone and later integrated into your larger system.

o Work closely with the community, on the #haskell IRC channel and the Haskell Cafe mailing list, to get guidance from experienced Haskellers. Share and discuss your code as you go along.

(Or, if you select a different language that you are not very experienced in for developing large high-assurance commercial systems, do the same with that language's community.)

...

Also there has been some concerns because of lazy evaluation in Haskell and memory leaks associated with it.

The possibility for memory and performance leaks in large systems written in Haskell is no more or less than in any other mature programming language. As in any language, it takes experience and care to avoid them as your application scales up.

Good luck, Yitz _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

On Wed, Jun 23, 2010 at 2:30 PM, Paul Johnson wrote:

On 15/06/10 09:08, Amiruddin Nagri wrote:

...

I wanted some insight as to how Haskell is going to help me with my project. Also there has been some concerns because of lazy evaluation in Haskell and memory leaks associated with it. http://jlouisramblings.blogspot.com/2010/04/haskell-vs-erlang-for-bittorent-...

In this talk:

http://www.galois.com/blog/2009/04/27/engineering-large-projects-in-haskell-... Don Stewart says that memory leaks are a tractable problem. Just profile and look for the retainers.

Lazy evaluation is a big win for large projects because it lets you modularise your solution; one function generates a data structure, and another function (or several) consume it. If the data structure is big or infinite then conventional languages force you to either interleave the generator and consumer, or else jump through lots of hoops re-inventing lazy evaluation on a case-by-case basis. With Haskell you just say what you mean and let the compiler worry about implementing it.

I think there are times when, in Haskell, you end up jumping through hoops to get specific performance characteristics (iteratees for example), but it appears to be the exception. Usually evaluation on demand gives you what you want and typically adding strictness in a few places fixes any leakiness. So, while Haskell is not perfect it gives you what you want more often than not. This translate directly into productivity gains. It also means that programmers tend to be happier using Haskell as they are fighting the notation less. Happy and productive is a win, even if you have to have a period of optimization at the end of the release cycle. I'd rather optimize correct code than start with a fast buggy version. I think at this point, the biggest weakness is that the tools for ensuring properties about space and time usage are far less mature than our tools for ensuring correctness. How would you formally specify your space or other performance needs? On the other hand, our profiling tools are quite good (ghc heap profiler, threadscope, criterion, etc) so as Don says, the problem is tractable. Jason