Alexy, This is a subject near and dear to my heart and I also dabble in Lisp and Erlang. Google for "Composing Financial Contracts", you will surely like the paper. This is the paper that got me started with Haskell. I'm sure you could do financial data mining in either Lisp, Haskell or OCaml. I think what matters most is being able to "compose" and specify what you want to do as opposed to how. You could compose your contracts in Lisp but it would not be as elegant as in Haskell. You would need to deal with layers and layers of macros, wrapping your head around the prefix notation and having to add laziness to prevent your data structure from always being evaluated. Lastly, you would want to apply different methods to your engineered contracts, e.g. to price them or print them as documents. There's no pattern matching in Lisp or guards for that matter. This means that you would need to resort to lots of imperative code and case statements that check the type of the data structure passed in to special-process it. Yes, you could add pattern matching to Lisp but it's not natural or that elegant. Yes, you could accomplish the same goal with CLOS, i.e. objects and methods. You could do the same in C++, Python or many other languages. Haskell is uniquely suitable for financial engineering. The boon of Haskell is being able to build a lazy data structure in memory to describe your financial contract, then use pattern matching and guards to deconstruct this data structure and slice it and dice it as you see fit, without having to evaluate it fully and running out of memory in doing so. The boon Haskell is being able to do this cleanly, elegantly and succinctly, without the need for extra helping layers of code. The bane of Haskell is not being able to predict the performance in doing the above. This may not be the reason why Yaron chose to use OCaml at Jane St a few years ago but this is certainly the reason why anyone would hesitate to use Haskell for the same purpose now. Haskell performance optimization is still black art and a few bits of magic. Joel -- http://wagerlabs.com/