time-consuming and it takes months in R. I like the language very much so far, but I do miss some important functions in R which can generate ^ typo ? ;) But for rnorm, if I use "foreign import ccall rnorm :: Double -> Double -> IO Double", then my main function should carry IO monad all the time. Maybe the better way is that I should "encapsulate" it into a state monad rng -> (rng, randomnumber). Therefore for rnorm, I should first write a wrapper in c like seed2 rnorm_wrapper(seed1, parameters){ set_seed(seed1); rnorm(parameters); get_seed(seed2); } set_seed rnorm get_seed doesn't have any side effect as long as you consider this sequence beeing atomic. If you don't use multithreading it should work fine. If you want to use multithreading have a look at http://haskell.org/haskellwiki/GHC/Concurrency, especially at "Software Transactional Memory (STM)" which is what you might need here (?) and then write another wrapper for rnorm_wrapper in haskell.
Can somebody tell me if this is the right approach? Thank you!
Have a look at (haskell.org -> library and tools -> Mathematics (http://haskell.org/haskellwiki/Libraries_and_tools/Mathematics) library "Probabilistic Functional Programming" Perhaps this lib does exactly what you need. There is another important source of packages: http://hackage.haskell.org/packages/archive/pkg-list.html Which way to go? I'm not a haskell expert so I can't tell you. It depends on what you need and how much time you want to spent on this topic ;) hope this helps Marc Weber