How to implement a global counter using Monad?

Question

I need a global counter, starting from 0, 1, 2, 3, ..... I kind of understand that this \"impure\" code should be separately implemented... I am just starting to understand

Answer 1

While State is fine, you don't need to inspect the counter while calculating, but just to increase it, so the Writer monad should be sufficient. See Learn you a Haskell for a (not too serious) introduction.