Scala 运算符的奇怪之处

Question

当我在 2 上调用 + 时，我会返回一个 Int，但是当它使用显式方法调用完成时，我会得到 Double。

scala> 2+2
res1: Int = 4

scala> 2.+(2)
res2: Double = 4.0

似乎 .+() 是在隐式转换为 Double 的 Int 上调用的。

scala> 2.+
<console>:16: error: ambiguous reference to overloaded definition,
both method + in class Double of type (x: Char)Double
and  method + in class Double of type (x: Short)Double
match expected type ?
              2.+
                ^

为什么呢 ？

Answer 1

在 Scala 2.9 及之前版本中，2.被解释为 2.0所以不明确的点表示浮点文字。您可以使用语法 (2).+(2) 显式调用该方法。 .

然而，模糊浮点语法将在 2.10 中被弃用:

scala> 2.+(2)
<console>:1: warning: This lexical syntax is deprecated.  From scala 2.11, a dot will only be considered part of a number if it is immediately followed by a digit.
       2.+(2)
       ^
<console>:2: warning: This lexical syntax is deprecated.  From scala 2.11, a dot will only be considered part of a number if it is immediately followed by a digit.
              2.+(2)
              ^
<console>:8: warning: This lexical syntax is deprecated.  From scala 2.11, a dot will only be considered part of a number if it is immediately followed by a digit.
              2.+(2)
              ^
res1: Double = 4.0