- how could I program something like this in Haskell: .. generate random population
Since Haskell is a "pure" language, after you attribute a value to a variable they are glued together forever. So, the language itself can't have such a thing as a random number. (Here, someone with technical knowledge will probably correct me, but you get the poing.) Dealing with this (and other "outside world" stuff) requires learning how to deal with a special type construct called "Monad". It's the major step you will have to as a Haskell begginer. It's, though, extremely interesting, and extremely powerfull after you understand it.
- Although I always liked math, I no longer have the knowledge I used to have several years ago. Is this important to help program in this funcional language?
No. But if you like math, you're probably going to find links to really interesting math while you learn.
(...) is it easy to connect it to a Python (or C) library?
To C libraries the answer is yes. Actually, if I want to do C, I prefer to do it in Haskell :) A friend of mine, who uses neural networks in his MSc work, was impressed that in half an hour I could get better results using a low-level binding from libfann to Haskell (link below) than his own hand written code. http://hackage.haskell.org/package/bindings-fann
- Is code easily reusable in different future projects? Since it has no objects... how can it be done?
Yes, to a point you may find too radical at first. Even the most basic constructs are usually combinations of other pieces. After some time, you will start any code you write by searching pieces to join together instead of writing everything yourself. It is, though, usually easier to write code from scratch in Haskell than reuse code in imperative languages :) Biased opinions, of course, but I hope they help. Best, Maurício