Scala Postfix运算符警告与Scaladoc相矛盾

Question

我的代码： val exitStatus = url #> outfile !

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

WTF ???

Answer 1

保持冷静并遵循警告。

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

而且......没有警告！ ：）

这样做的原因是，Scala的新手不会意外地使用这些并最终对语法更加困惑。我不确定我同意这个理由，但它似乎与我的同事/朋友一起工作，所以肯定会有一些东西。

旁边here是Scaladoc页面，详细介绍了所有这些内容。您也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