module RecordIterator;

trait
type Foldable (container elem : Type) :=
  mkFoldable@{
    syntax iterator for {init := 1; range := 1};
    for : {B : Type} -> (B -> elem -> B) -> B -> container -> B;

    syntax iterator rfor {init := 1; range := 1};
    rfor : {B : Type} -> (B -> elem -> B) -> B → container → B;
  };

open Foldable;

foldl
  {container elem}
  {{Foldable container elem}}
  {B : Type}
  (g : B -> elem -> B)
  (ini : B)
  (ls : container)
  : B :=
  for (acc := ini) (x in ls) {
    g acc x
  };