tail-call-babel.js

// file: tail-call-babel.js
'use strict';
// #1 "naive"
function factorial1(x) {
  if (x <= 0) {
    return 1;
  } else {
    return x * factorial1(x - 1);
  }
}

// #2 tail rec using a default parameter
function factorial2(n) {
  return facRec2(n);
}
function facRec2(_x2) {
  var _arguments = arguments;
  var _again = true;

  _function: while (_again) {
    var x = _x2;
    _again = false;
    var acc = _arguments.length <= 1 || _arguments[1] === undefined ? 1 : _arguments[1];

    if (x <= 1) {
      return acc;
    } else {
      _arguments = [_x2 = x - 1, x * acc];
      _again = true;
      acc = undefined;
      continue _function;
    }
  }
}

// #3 tail rec
function factorial3(n) {
  return facRec3(n, 1);
}
function facRec3(_x3, _x4) {
  var _again2 = true;

  _function2: while (_again2) {
    var x = _x3,
        acc = _x4;
    _again2 = false;

    if (x <= 1) {
      return acc;
    } else {
      _x3 = x - 1;
      _x4 = x * acc;
      _again2 = true;
      continue _function2;
    }
  }
}