Question

请参阅https://www.scala-lang.org/files/archive/spec/2.11/02-identifiers-names-and-scopes.html的示例，我注意到在示例中package P被定义了两次。这个例子不正确吗？我试图在Scastie中运行它，但是代码无法编译。

https://scastie.scala-lang.org/ZZ3vjsNzSvWnY1gFCqaNAg

    package P {
      object X { val x = 1; val y = 2 }
    }

    package Q {
      object X { val x = true; val y = "" }
    }
//    The following program illustrates different kinds of bindings and precedences between them.

//isn't this redefining P??    
    package P {                  // `X' bound by package clause
    import Console._             // `println' bound by wildcard import
    object A {
      println("L4: "+X)          // `X' refers to `P.X' here
      object B {
        import Q._               // `X' bound by wildcard import
        println("L7: "+X)        // `X' refers to `Q.X' here
        import X._               // `x' and `y' bound by wildcard import
        println("L8: "+x)        // `x' refers to `Q.X.x' here
        object C {
          val x = 3              // `x' bound by local definition
          println("L12: "+x)     // `x' refers to constant `3' here
          { import Q.X._         // `x' and `y' bound by wildcard import
    //      println("L14: "+x)   // reference to `x' is ambiguous here
            import X.y           // `y' bound by explicit import
            println("L16: "+y)   // `y' refers to `Q.X.y' here
            { val x = "abc"      // `x' bound by local definition
              import P.X._       // `x' and `y' bound by wildcard import
    //        println("L19: "+y) // reference to `y' is ambiguous here
              println("L20: "+x) // `x' refers to string "abc" here
    }}}}}}

Answer 1

例如，它不是重新定义，而是添加到软件包package P { object X { val s = "hello"} } package P { object Y { val s = "world"} } object Hello extends App { println(P.X.s) println(P.Y.s) }

hello
world

输出

这意味着Y和P现在可以从软件包requests中获得

一个示例如何具有两个具有相同名称的软件包

1 个答案: