这是一个协程,可以避免像(chain(m)(chain(…)))这样的嵌套模式进行单子计算：

const some = x => none => some => some(x);
const none = none => some => none;

const option = none => some => tx => tx(none) (some);
const id = x => x;

const of = some;
const chain = fm => m => none => some => m(none) (x => fm(x) (none) (some));

const doM = (chain,of) => gf => {
  const it = gf();

  const loop = ({done,value}) =>
    done
      ? of(value)
      : chain(x => loop(it.next(x))) (value);

  return loop(it.next());
};

const tx = some(4),ty = some(5),tz = none;

const data = doM(chain,of) (function*() {
  const x = yield tx,y = yield ty,z = yield tz;

  return x + y + z;
});

console.log(
  option(0) (id) (data)); // 0

但是我无法为应用计算实现等效的协程：

const some = x => none => some => some(x);
const none = none => some => none;

const option = none => some => tx => tx(none) (some);
const id = x => x;

const of = some;
const map = f => t => none => some => t(none) (x => some(f(x)));
const ap = tf => t => none => some => tf(none) (f => t(none) (x => some(f(x))));

const doA = (ap,value},initial) =>
    done
      ? value
      : ap(of(x => loop(it.next(x)))) (value);

  return loop(it.next());
};

const tx = some(4),tz = none;

const data = doA(ap,z = yield tz;

  return x + y + z;
});

console.log(
  option(0) (id) (data)); // none => some => ...

这应该可以,但是不能.附加的函子包装来自何处？我想我在这里的递归有点迷路了.

顺便说一下,我知道这仅适用于确定性函子/单子.