type storage = (int, list(int));

type parameter = list(int);

type return = (list(operation), storage);

let x: list(int) = [];

let y: list(int) = [3, 4, 5];

let z: list(int) = [2, ...y];

let main = 
  (((action, s): (parameter, storage))): return => 
    {
      let storage = 
        switch(action) {
        | [] => s
        | [hd, ...tl] => (s[0] + hd, tl)
        };
      ([] : list(operation), storage)
    };

let size_ = ((s: list(int))): nat => List.length(s);

let fold_op = 
  ((s: list(int))): int => 
    {
      let aggregate = ((t: (int, int))) => t[0] + t[1];
      List.fold(aggregate, s, 10)
    };

let map_op = 
  ((s: list(int))): list(int) => 
    List.map(((cur: int)) => cur + 1, s);

let iter_op = 
  ((s: list(int))): unit => 
    {
      let do_nothing = ((useless: int)) => unit;
      List.iter(do_nothing, s)
    };