scala - 隐含点和括号的Scala优先级

Question

以下“括号”如何？

val words = List("foo", "bar", "baz")
val phrase = "These are upper case: " + words map { _.toUpperCase } mkString ", "

是不是一样

val words = List("foo", "bar", "baz")
val phrase = "These are upper case: " + words.map(_.toUpperCase).mkString(", ")

换句话说，隐含的点（“.”）和括号是否与真实的具有相同的优先级？

第一个版本是否与第一个版本相同

val words = List("foo", "bar", "baz")
val phrase =
  "These are upper case: " + (words map { _.toUpperCase } mkString ", ")

score 4 · Accepted Answer

以字母开头的运算符的优先级最低。+具有低优先级但高于mapor mkString。所以

"These are upper case: " + words map { _.toUpperCase } mkString ", "

应该被解析为：

(("These are upper case: " + words).map{ _.toUpperCase }).mkString(", ")

把它想象成：

v1 + v2 map v3 mkString v4
((v1 + v2) map v3) mkString v4

有关更多信息，请参阅我的其他答案：When to use parenthesis in Scala infix notation

1 回答 1