Question

I have this recursive function:

def lifecycle(population):
    ...
    lifecycle(new_population)

I want to perform this loop 100 times. I want to use correct functional style. So, I cannot use a counter? Because assigning new values to a variable is not okay in functional programming. How does one do this functionally? I’m using Python.

Answer 1

Technically, like this:

def lifecycle(population, i):
    if i == 100:
        return ...
    ...
    return lifecycle(new_population, i + 1)

But this is a really, really silly thing to do in Python (and it fails for all but the smallest examples, due to tail calls being not optimized). Just use a loop, although that uses mutable state under the hood, the remaining program can be perfectly functional.