collatz.dito

# collatz.dito:
# Program defines a function that given a start
# position will create a collatz sequence from start - 1
# this value is returned as an array.
# ---------------------------------------------------------------------
# using `append` and `last`
import std

def main() {
    print(collatzSequence(35))
}

def collatzSequence(start) {
    # define an array with our start item.
    let mut seq = [start]
    # use a while style for loop to keep adding to the sequence.
    # checking the item at the last index of the sequence.
    let mut curr = last(seq)
    for curr > 1 {
        # Get the next value in the sequence.
        let newitem = collatz(curr)
        # Append each new item to array.
        seq = append(seq, newitem)
        curr = last(seq)
    }
    return seq
}

# define a lambda function that can only be a single expression.
# here it uses a if else expression like what can be found in python.
let collatz = def(n) -> (
    n           if n <= 1 else
    n // 2      if n % 2 == 0 else
    3 * n + 1)