TRMC in Elm

a.js

/* Corresponds to the following Elm code

map fn list =
    case list of
        [] -> []
        x :: xs ->
            fn x :: map fn xs

*/

var map = function (fn, list) {
  if (!list.b) {
    return _List_Nil;
  } else {
    var x = list.a;
    var xs = list.b;
    return cons(
      fn(x),
      map(fn, xs)
    );
  }
};


var map = function (fn, list) {
  var $start = _List_Cons(undefined, _List_Nil);
  var $end = $start;
  map: while (true) {
    if (!list.b) {
      return $start.b;
    } else {
      var x = list.a;
      var xs = list.b;
      $end = $end.b = _List_Cons(fn(x), _List_Nil);
      list = xs;
      continue map;
    }
  }
}


// For comparison, this is a plain tail recursive function (this function is useless though)

// Elm
foo : List a -> List b
foo list =
    case list of
        [] ->
            []
        _ :: xs ->
            foo xs

// JavaScript
var foo = function (list) {
  foo: while (true) {
    if (!list.b) {
      return _List_Nil;
    } else {
      var xs = list.b;
      list = xs;
      continue foo;
    }
  }
};