Like others said before: CL is just a programming language that can be used for functional programming, but doesn't enforce this. So you have to be disciplined

Like others said before: CL is just a programming language that can be used for functional programming, but doesn't enforce this. So you have to be disciplined. I stick to the following rules: * have a (main) function * prefix io functions with io- and only use them in (main) (inspired by Haskell) * No loop. Always recursion. * No variables. No local ones and definitely no global ones. That way, you have to think more in functional terms than in imperative ones. Helps me. Your mileage might vary.