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 ", "

与

相同

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

换句话说，隐含的点（“。”）和括号是否与实际的优先级相同？

第一个版本是否与

相同

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

Answer 1

以字母开头的运算符具有最低优先级。 +优先级较低，但高于map或mkString。所以

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

应解析为：

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

将其视为：

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

有关详细信息，请参阅我的其他答案：When to use parenthesis in Scala infix notation