Scala Postfix 运算符警告与 Scaladoc 相矛盾

Question

我的代码:val exitStatus = url #> 输出文件!

scala.sys.process :new URL("http://www.scala-lang.org/") #> new File("scala-lang.html") !

警告:

postfix operator ! should be enabled
[warn] by making the implicit value scala.language.postfixOps visible.
[warn] This can be achieved by adding the import clause 'import scala.language.postfixOps'
[warn] or by setting the compiler option -language:postfixOps.
[warn] See the Scaladoc for value scala.language.postfixOps for a discussion
[warn] why the feature should be explicitly enabled.
[warn]     val exitStatus = url #> outfile !
[warn]                                     ^
[warn] one warning found

什么鬼？？？

Answer 1

保持冷静并遵守警告。

import scala.language.postfixOps
...
val exitStatus = url #> outfile !
...

而且...没有警告! :)

这样做的原因是，Scala 的新手不会无意中使用它们而最终对语法更加困惑。我不确定我是否同意这个理由，但它似乎与我的同事/ friend 一起工作，所以肯定有一些东西。

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题外话here是详细说明所有这些的 Scaladoc 页面。您还可以将它们作为编译器标志或通过 build.sbt 启用。

-language:dynamics             # Allow direct or indirect subclasses of scala.Dynamic
-language:existential          # Existential types (besides wildcard types) can be written and inferred
-language:experimental.macros  # Allow macro defintion (besides implementation and application)
-language:higherKinds          # Allow higher-kinded types
-language:implicitConversions  # Allow definition of implicit functions called views
-language:postfixOps           # Allow postfix operator notation, such as `1 to 10 toList'
-language:reflectiveCalls      # Allow reflective access to members of structural types