Scala 语法奇怪与 :: 并需要小写 [英] Scala syntax strangeness with :: and requiring lower case
问题描述
这是应该发生的吗?
scala> val myList = List(42)
myList: List[Int] = List(42)
scala> val s2 :: Nil = myList
s2: Int = 42
scala> val S2 :: Nil = myList
<console>:8: error: not found: value S2
val S2 :: Nil = myList
^
它似乎区分大小写.错误或功能"?
It appears to be case sensitive. Bug or 'feature'?
推荐答案
区分大小写.在匹配模式中，以大写字母开头(或用反引号引用)的标识符被视为对已定义值的引用，而不是新绑定.
It is case-sensitive. In a match pattern, an identifier beginning with a capital letter (or quoted by backticks) is treated as a reference to a defined value, not as a new binding.
这让很多人感到惊讶，阅读 Scala 语言规范并不完全清楚.最相关的位是 “可变模式”...
This catches a lot of people by surprise, and it isn't entirely obvious from reading the Scala language specification. The most relevant bits are “variable patterns” ...
变量模式 x 是一个以小写字母开头的简单标识符.它匹配任何值，并将变量名绑定到该值.
A variable pattern x is a simple identifier which starts with a lower case letter. It matches any value, and binds the variable name to that value.
... 和 “稳定的标识符模式”:
... and “stable identifier patterns”:
为了解决与变量模式的句法重叠，稳定的标识符模式可能不是以小写字母开头的简单名称.
To resolve the syntactic overlap with a variable pattern, a stable identifier pattern may not be a simple name starting with a lower-case letter.
相关问题:
这篇关于Scala 语法奇怪与 :: 并需要小写的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
