reason1.re

type result 'a = {mutable list: list 'a};

let firstN (n: int) (l: list 'a) :list 'a => {
  let result: result 'a = {list: []};
  let start = 0;
  let stop = min (n - 1) (List.length l - 1);
  for i in start to stop {
    result.list = List.append result.list [List.nth l i]
  };
  result.list
};

firstN 2 [1, 2, 3, 4, 5]; /* => list int: [1, 2] */