trampoline-vs-fix.js

/*** FIX ***/
var fix = f => x => f(fix(f))(x);


/*** TRAMPOLINE ***/

const rec = (...args) => ({ rec: true, args });
const ret = x => ({ rec: false, x });

var trampoline = f => (...args) => {
  var res = f(...args);

  while (res.rec) {
    res = f(...res.args);
  }

  return res.x;
}

/*** SUM ***/

var sumTramp = xs => trampoline((acc, i) =>
  i === xs.length
    ? ret(acc)
    : rec(acc + xs[i], i + 1))(0, 0)

const sumFix = fix(rec => acc => i => xs =>
  i === xs.length
    ? acc
    : rec(acc + xs[i])(i + 1)(xs))(0)(0);

/** MAIN ***/
const mainFix = sumFix([1, 2, 3, 4, 5]);

const mainTramp = sumTramp([1, 2, 3, 4]);

console.log('trampoline sum', mainTramp);
console.log('fix sum', mainFix);