My goal is to create an infinite list by applying a function to the last element. For example if I begin with a list that looks like
[1]
and apply the function f(x) = (x + 2) * 10, I should end with
[1, 30, 320, 3220, 32220...]
How would I code this in Haskell?
There's iterate
iterate :: (a -> a) -> a -> [a] -- Repeat a function forever, making a list of values
If you want to start with a list and only operate on its last element:
func f xs = (init xs) ++ (iterate f $ last xs)
You've already got your answer: you use iterate. Here's how you can code it yourself.
iterate takes a function f and a seed x, and repeats function application forever (i.e. returns [x, f x, f (f x), f (f (f x)), ...])
iterate :: (a -> a) -> a -> [a]
iterate f x = x : map f (iterate f x)
iterate f (f x) instead of map f (iterate f x)?
iterate f x = ys where ys = x : map f ys should be better.