function _curry2(fn) {
    return function f2(a, b) {
      switch (arguments.length) {
        case 0:
          return f2;
        case 1:
          return _isPlaceholder(a) ? f2 : _curry1(function (_b) {
            return fn(a, _b);
          });
        default:
          return _isPlaceholder(a) && _isPlaceholder(b) ? f2 : _isPlaceholder(a) ? _curry1(function (_a) {
            return fn(_a, b);
          }) : _isPlaceholder(b) ? _curry1(function (_b) {
            return fn(a, _b);
          }) : fn(a, b);
      }
    };
  }
Optimized internal two-arity curry function.

@private
@category Function
@param {Function} fn The function to curry.
@return {Function} The curried function.