function _createPartialApplicator(concat) {
    return _curry2(function (fn, args) {
      return _arity(Math.max(0, fn.length - args.length), function () {
        return fn.apply(this, concat(args, arguments));
      });
    });
  }
Takes two arguments, `fst` and `snd`, and returns `[fst, snd]`.

@func
@memberOf R
@since v0.18.0
@category List
@sig a -> b -> (a,b)
@param {*} fst
@param {*} snd
@return {Array}
@see R.objOf, R.of
@example

     R.pair('foo', 'bar'); //=> ['foo', 'bar']