Is there a problem with curryN?

[王玄]

const curriedAdd = R.curryN(3, (a, b, c) => { return a + b + c })
console.log(curriedAdd(1, R.__, R.__, R.__, R.__, R.__)(R.__, R.__)(3, R.__)(R.__)(4))

I understand that the result should be returned at this time, but the function is returned

Should this be adjusted?

while (combinedIdx < received.length || argsIdx < arguments.length) {
  var result;
  if (combinedIdx < received.length && (!_isPlaceholder(received[combinedIdx]) || argsIdx >= arguments.length)) {
    result = received[combinedIdx];
  } else {
    result = arguments[argsIdx];
    argsIdx += 1;
  }
  if (!_isPlaceholder(result)) {
    left -= 1;
    combined[combinedIdx] = result;
    combinedIdx += 1;
  } else {
    hasPlaceholder = true;
  }
}

[Matthias Seemann]

calling a function fn = curryN(N, f) with the placeholder __ as (N+1)th argument certainly breaks fn.

In good JS fashion extra arguments to a function should be ignored — but __ seems to be an extreme edge case.

Is that worth fixing?
i.e What is the use case in your code?

[王玄]

I think this doesn't matter

  function _curryN(length, received, fn) {
    return function () {
      var combined = [];
      var argsIdx = 0;
      var left = length;
      var combinedIdx = 0;
      var hasPlaceholder = false;
      while (combinedIdx < received.length || argsIdx < arguments.length) {
        var result;
        if (combinedIdx < received.length && (!_isPlaceholder(received[combinedIdx]) || argsIdx >= arguments.length)) {
          result = received[combinedIdx];
        } else {
          result = arguments[argsIdx];
          argsIdx += 1;
        }
        combined[combinedIdx] = result;
        if (!_isPlaceholder(result)) {
          left -= 1;
        } else {
          hasPlaceholder = true;
        }
        combinedIdx += 1;
      }
      return !hasPlaceholder && left <= 0 ? fn.apply(this, combined) : _arity(Math.max(0, left), _curryN(length, combined, fn));
    };
  }

Why not eliminate the placeholder in this function execution, but in the next execution? What are the considerations?

[Kevin Wallace]

Do you have a valid use case for this @xuanWangisAlibaba19960403 ? I can't really think of one, but if you have a fix which does not degrade performance we can consider a PR.