Scala中部分应用的isBefore函数给出错误

我正在尝试在Scala中合并两个日期序列，以便合并后的序列具有排序元素。我正在使用isBefore的部分实现，如下所示：

  val seq1 = Seq(LocalDate.of(2014, 4, 5), LocalDate.of(2013, 6 ,7), LocalDate.of(2014, 3, 1))
  val seq2 = Seq(LocalDate.of(2012, 2, 2), LocalDate.of(2015, 2, 1))
  var arr = (seq1 ++ seq2).sortWith(_.isBefore(_) = 1)
  println(arr)

但它显示isBefore函数的编译错误：

 Multiple markers at this line
- missing arguments for method isBefore in class LocalDate; follow this method with `_' if you want to 
 treat it as a partially applied function
- missing arguments for method isBefore in class LocalDate; follow this method with `_' if you want to 
 treat it as a partially applied function

---

我对Scala比较陌生。问题似乎出在哪里？

起初没有“部分实现”这样的术语，至少我没听说过，我猜你指的是“部分应用”，但在这种情况下，没有“部分应用”，部分应用是关于curried函数的，编译器试图在错误消息中告诉你什么。例如：

def test(a: String)(f: String => String) = f(a)

val onString = test("hello world") _

onString(_.capitalize)

test: (a: String)(f: String => String)String
onString: (String => String) => String = <function1>
res8: String = Hello world

val seq1 = Seq(LocalDate.parse("2014-04-05"), LocalDate.parse("2013-06-07"), LocalDate.parse("2014-03-01"))
val seq2 = Seq(LocalDate.parse("2012-02-02"), LocalDate.parse("2015-02-01"))
var arr = (seq1 ++ seq2).sortWith(_.isBefore(_))

arr: Seq[org.joda.time.LocalDate] = List(2012-02-02, 2013-06-07, 2014-03-01, 2014-04-05, 2015-02-01)